Oh shame we'll be away when you're there or else I could have shown you around as we own a static caravan on the site.
The swimming pool is lovely, on site, not too deep so non-swimmers are well catered for. Also, at 10am and 2pm there is entertainment for the kids, at the family Fun Bar - say hi to Kerry from me (Enid's mum ).
Rye has a soft play area, in the car park where the market is (a couple of days a week). Also, if you can, take the train to Hastings from Rye, so much more less hassle than driving and my kids love it. Hastings has a cable car, cinema, sea world, clambers play area.
Also, if you're blessed with good weather, try and go on the A259 (up towards Folkestone) to Dymchurch. Lovely old fair ground rides catered for the younger kids (and not too expensive like Hastings).
Oh and I've just remembered, you might not be able to get into Rye - they are closing off the bridge from a259 (Camber side) into Rye for road-works. They are meant to take place for the whole of October, so check first.
Have a lovely time - the 4 days will speed by and all your plans will have gone out the window, I can guarantee.