Sixty children in care will get together for what's being billed as a giant party or play date on Saturday - but some of them know that when they leave they may have found what they most want in the world - parents or a new family of their own.
Aged from one to nearly eight, the children will get the chance to try out juggling and other circus skills in a 'Big Top day' aimed at being fun - with a purpose.
Those who are said to be "old enough to understand" will know that some of the grown-ups chatting to them as they play games or do crafts want to adopt a child, with children as young as three or four being told what the day is all about.
Activity days - sometimes dubbed Adoption parties - have attracted controversy, being described by some as cattle markets, or adoption speed-dating.
They were run in the UK for a time from the mid-1970s, but have been held in the USA for more than 30 years.
Now they have returned to the UK, with a pilot scheme involving nine local authorities and several adoption agencies.
They are organised by the British Association for Adoption and Fostering (BAAF) - in partnership with some councils and voluntary adoption agencies. The first event was in January 2011 and the fourth is this weekend.
'A fun event'
Bridget Betts, who is in charge of the activity days for BAAF, says "matches" have been made for 23 out of the 120 children who have been to the three events held so far.
"For most of the children who are attending, other traditional methods of family-finding have not worked, so these are children who would otherwise have not had a family," she said.
Traditionally, people wanting to adopt would have been shown written profiles, pictures and videos of children. Because of the risk of giving a vulnerable child false hope or further disappointment, they often do not get to meet them until the adoption process is well advanced.
Bridget Betts says the US experience convinced her of the worth of the events: "Statistics show adoption activity days are twice as effective as other ways of family-finding for children.
"Adopters get to see children enjoying themselves, having fun and see them first as children without reading about all their problems.
"The emphasis for the day is about fun for the children. They have a proper invitation for the day and at the end of the day they go home with a party bag."
For Alice and Mark (not their real names), the last such event, earlier this year, may have brought them their own family.
"We did not go there thinking we were going to meet our kids; we thought we would see the kind of children who were waiting to be adopted," said Alice.
"But almost the first children we saw... they were absolutely lovely... for some reason I thought 'These are our kids'."
The couple say would-be adopters were encouraged to interact with the children, to talk to them and play with them but were told not to stay too long with anyone in case it raised their expectations.
They say they enjoyed meeting the other children, but kept thinking about those two - and later went back to them.
There was "chemistry" which they would not have been able to get through a paper profile of a child, they said.
The couple are now in the process of trying to adopt the children.
"It was fun; a huge party. They had a boat, archery, water cannon. And it was well structured - with staff everywhere, passively watching," said Mark.
The party worked like this: They were teamed up with a social worker, while children had either their social worker, foster carer or another adult with them.
If they saw children they were interested in meeting, their social worker would talk to the children's social worker and arrange it.
Risk of rejection
Adoption speed dating by proxy? Possibly. It is that "fast" aspect - and the potential danger of vulnerable, damaged children facing further hurt - that worries some people.
Bridget Betts from BAAF says that is a danger everyone involved is all too aware of: "These are vulnerable children and the risk of rejection and being rejected again is quite high and for some of those children, social workers and their foster carers have had to support them afterwards.
"What is good about this is is it has to directly involve the children; you can't do it behind their backs and they can see that the adults around them are doing everything they can to find a family for them."
Voices have been raised against such days in the UK. Last year, Barnardo's chief executive Anne Marie Carrie, was critical of the idea on BBC Radio Four's Woman's Hour, saying "This is not Battersea Dogs Home. I am concerned about this aspect of beauty parades.
"What happens when a child has been to 10 parties?"
But are children's charities warming to this approach?
The NSPCC's Tom Rahilly - head of looked-after children - says the events make sense as the next logical step on from looking at photos of children and forms - but they have to be carefully planned and delivered.
"Adoption activity days are an opportunity for groups of prospective adopters and children waiting to be adopted together in person before any decisions have been made," he said.
"They make the experience and potential much more real, particularly for prospective adopters who can live in a very theoretical world right up until the day they meet their new child for the first time."
For writer Anne (not her real name), who adopted two young boys about eight years ago with her husband, the idea of meeting lots of children waiting to be adopted seems "awful".
"It's an American idea and the parties have been criticised there for putting children on show, making it like an audition. Here, the idea has been to try to make sure that a match will work before introducing everyone.
"We did not meet our children until we had been matched with them.
"The first glimpse we had of them was when there was no pressure on either side - they didn't know we were watching them. We were told to go to a playground at a certain time and they were brought there with other kids to play.
"We sat on a bench, reading a newspaper, feeling a bit furtive watching them, but it was nice to see them being themselves, calling to each other."
Speeding up the adoption process and getting more children adopted has been made a priority by the government in England.
Prime Minister David Cameron has said too few children are being given the chance of a finding the security of a stable permanent home. Councils are being more closely monitored and there are controversial new "adoption league tables".
Only a small proportion of the 67,000 children in care in England are available to be adopted. Many go in and out of care as their family circumstances change, while arrangements might be made for others to be looked after by grandparents or other family members.
There were 3,450 looked-after children adopted in the year ending 31 March 2012 - the highest figure since 2007.
Adoption experts say children are much less likely to be adopted if they are older, with brothers or sisters or have disabilities.
BAAF's Bridget Betts says the adoption activity days help to open the eyes of potential adopters to such children.
"For adopters, it dispels the myths about children who are in care. Most adopters start out thinking 'I would like a pre-school child', but they might meet a seven-year-old," she said.
"We had one little girl matched from the first day where every method of matching had failed. She had very complex needs and a lot of uncertainty about her future. Some adopters came who had not thought about adopting a child with additional needs - and she is now placed with them."
Could such examples be winning over sceptics?
In a statement this week, Barnardo's UK director of strategy Janet Grauberg, said: "Finding a loving and secure adoptive family for these children is critical. We welcome any approach that encourages prospective adoptive parents to consider again whether they could provide a home for an older child or a sibling group.
"Of course, it is also vital that safeguards are in place to ensure the emotional safety of these children during such a vulnerable stage of their lives."
Adoption activity day project manager Bridget Betts says she understands why some people react against the idea of the days.
"For all parties who come it's a very emotional experience and everyone needs preparation and support," she said.
"I find it quite overwhelming and a very emotional experience as a social worker with 30 years' experience - walking in to a room with 60 children who need adopting - and they are all beautiful children."