Hi.
Haven, Butlins even Pontins all do holidays with activities geared at children.
I have found Norfolk to be good for children i have holidayed along the coast for many years from Searles at Hunstanton << My No1 Choice

to Great Yarmouth, Cromer, Heacham, Wells, even as far down as Lowerstoft. The area is nice and the big holiday camps have lots of stuff for adults aswell as children. Some do Self catering and others also offer Half board which eases the strain of cooking everyday
I'm not sure if i'd be allowed to mention it on the site but there are a few review sites around that will let you know of other's experiences of different places arounf the UK.
PM me if you want links for ideas
