Good old-fashioned games can always help with boredom, frustration and arguments. Kids love looking out of the window, so play simple games to keep them entertained. You can play the classic version of I Spy or make it into a counting game by seeing how many different things you can see, such as how many red cars can you spot?
You can even practice the alphabet with 'car registration plate bingo' where you use car registration plates to run through the alphabet. So for the little ones, get them to call out as they see each letter on a passing car. For the older kids, you can try to spot the letters in the correct order to make the game last longer.
Make up a story; One person makes up the first line of the story, then you all take it in turns to say what happens next. Be as creative or silly as you like - who knows how your story will end!