They change it every year. A lot of it is seeing how the boys work together in groups, taking turns, listening to others, cooperating but also participating and contributing. There are sometimes things like maths patterns, how to make the shapes fit a particular picture, games with words/dice etc but it can't be prepared for. It shouldn't be stressful for anyone and definitely not the boys - they come out having had a good time, a bit of a play and having had a chocolate biscuit! Good luck to your sons.