We go to CP Elveden every year, my boys are 10 and 7, we always book badminton, tennis (indoor) bowling, rollerskating and this year, make a habitat.
In the past they have done mini crossbows and outing with owls which was fantastic, indoor climbing wall, horse and carriage ride, horse riding hmm that is all I can think of for now 
We go swimming every day including the day we arrive and the day we leave.
We try not to over-schedule as the boys love it but can become over tired. Plus we fit in starbucks every day as they love the chocolate creams they do, plus it helps re-fuel them.
We are going in November as we have an inset day, we usually go in May/June but it is Ds1's SATs year so we are going abroad then, hence why all our activities are indoors this time.
Agree about keep checking the booking page. We love CP as you can tell, we have sometimes even been twice in the same year. It isn't a holiday for me, but the boys enjoy it so much we indulge them.