Hi
Have a look at Unity in Brean, Somerset.
It has daytime childrens fun clubs and evening family entertainment, an indoor pool,cycle hire, pedal buggy's, horse riding etc and a large funfair next door which can be accessed via an underpass to prevent children straying into roadways.It has everything you need to keep children occupied whatever the weather, pitches are adequate and well drained now that a new drainage system is installed and the site is easy to get to, ten minutes from the M5.
Brean itself is not much to write home about but there are some interesting places to visit in Somerset.
The amenity blocks are heated and clean and for a very large commercial holiday site it is very well run. The site offers bargain breaks with discounts and a loyalty card.
I have no connection with the site but we stay there now and again.
http://www.hru.co.uk/home