I agree the messy play is expensive but they do have plastic animals in jelly, baked beans and pasta, painting, play-doh, water play etc so they make all the mess there and it is great fun.
We have been to Whinfell twice and are about to go back again!! We have also been to Sherwood 3 times and Elvedon once (although it is the best one it is a great trek for us)
The beauty of CPs is walking, cycling etc, the swimming pool is fab and the spa if you can get away for a few hours, the fact that you could walk back alone at night and not feel remotely vulnerable. It is almost like an exclusive club where you only find out everything about it when you get there!! A bike with a trailer would be great so your DD
can be sat in a covered little carriage.
Whinfell is very beautiful but a word on accommodation - "comfort" is incredibly basic and VERY dated, "comfort plus" is the same decor but you get a dishwasher, towels and a DVD player. The "Woodland lodge" of any description are the new renovated ones with very contemporary fixtures and fittings (guess which one I am going for!!!) with DVD player, dishwasher, towels etc. Executive is dated but more plush and each room has an en-suite bathroom. I have ony ever done comfort plus and executive.
The supermarket has a wide variety of stuff so don't feel you need to lugg everything with you. It is reasonably priced, the restaurants are a little expensive but you can decide how often you cook or eat out.
If you have any specific questions post on this and I will keep an eye on it and respond. I love Center Parcs, my two sons are almost 5 and almost 2, we have a great time every time we go.