I've taken the children to www.coombemill.com in North Cornwall several times before and we've had a fantastic time. It's super for children, has about 3 playgrounds on sight including an indoor one (soft play area so perfect for when mine were much younger!) There's a swimming pool just up the road, beach 20min drive, village shop 10min walk up the road (it is a steep hill!) The best part is the farm though, there are animal feed runs every morning where the children get to help ride the tractor and feed all the animal (they sit in a sort of trailer on the back of the tractor). DEFINITELY worth having a look as we absolutely love it and couldn't recommend it more Good luck!!
York lakeside lodges. Park and lake on site, 5 minutes walk to tesco and bus station to take you into York where there is lots to do (boat rides, Viking museum, national railway museum, markets, carousel, Bettys tea room)