Lawyers representing 28 victims of last year's E. coli outbreak at Godstone farm in Surrey are preparing to demand "substantial" damages in a group legal action.
Ninety-three people, mostly young children, were infected with the potentially deadly O157 strain of E. coli after visiting the farm.
Some are still ill with kidney damage.
Godstone farm says it cannot comment on the legal action until the release of a report into the outbreak due next week.
Two of the victims who are expected to be named in the legal action are twins Aaron and Todd Mock, who are about to celebrate their third birthday.
Both had kidney failure and spent weeks in hospital with E. coli poisoning after visiting Godstone Farm last September. Aaron is still unwell; he has limited kidney function and has to be given liquids through a feeding tube.
Their mother, Tracy, worries that he may have such badly damaged kidneys he will need a kidney transplant when he is older.
"At the moment we're just grateful that they're both happy. I don't know what the future holds for them," she told the BBC. "For now we're just enjoying our two little boys."
Their lawyer, Jill Greenfield, alleges that Godstone Farm was negligent in the way it handled the outbreak of E. coli O157. She is representing 27 children and one adult who were affected.
"This strain is very different from general E. coli," she said. "It's a potentially deadly bacteria that affects the young and the elderly. It's up to farms to give people the proper information about it."
She says it is impossible to know how many people will have long term consequences from the outbreak, and how long they will be affected.
"Once the kidneys are damaged they don't tend to repair themselves," she said.
Children will need kidney checks when they are five and as they reach adolescence, and could need dialysis or even a transplant when they get older.
Ms Greenfield said their financial needs could be very substantial.
"They have to have the money they need to help them live their lives."
Since last year's outbreak, the rules on E. coli O157 have changed, making some of its symptoms notifiable in the way smallpox or measles are. Doctors now have to notify the relevant authorities if they detect signs of the infection.
It is another development in a case that has sent a chill through open farms across the UK.
"It's been a wake-up call," said Bill Graham from the organisation Farming and Countryside Education. "It reminds all farms to ensure they have good hygiene measures in place."
There was a marked decline in the number of farm visits after the outbreak last September. He says it is important not to underestimate the impact that E. coli O157 poisoning can have but, at the same time, children could be losing out if they stop going to farms.
"You've only got to see their awe and wonder at what they're seeing. That's the real value - their first contact with countryside and animals helps their understanding of what farming is all about and where their food comes from."
Godstone Farm has re-opened and is busy with visitors again. Its owners are awaiting a report into the outbreak commissioned by the Health Protection Agency due next week before they make any comment on the legal action.