Have a look at sites around the Pickering area - we recently stayed at Upper Carr which was very nice - as you will be close to Dalby Forest for walking, cycling and horse riding, Go Ape and Flamingoland theme park.
Not sure how far you want to travel nor what facilities you actually want on site, but we camped at Evergreen campsite in East Grinstead over the bank holiday, and just up the road from there is a place called Blackland Farm http://www.ukcampsite.co.uk/sites/reviews.asp?revid=1920
They do all sorts of activities that sound exactly the kind of thing you are looking for. Evergreen is a very basic site though, only facilities being a couple of compost loos, so you may want to check out any other campsites in that area...
We might be heading across to Tallington Lakes, Lincs this weekend. Looks good has water sports to try, karting and climbing wall dry ski slope.
We tend to stay away from some larger sites but this close to home and we are going with virgin campers.