It's hard for me to judge because I've never been to a centre parks in the UK. We went to the one in Port Zealand and it certainly had it's pluses and minuses.
Plus : it was easy to drive to and having the car meant we could bring whatever we wanted.
The pool was fantastic and I think there was plenty of pool stuff appropriate for your kid's ages. They certainly have the kids and pool thing sorted.
Minus: the little houses weren't all that nice and we had even paid for an upgrade. You will have to bring EVERYTHING you will need, including salt and pepper. The grocery store there is vastly overpriced but you can go out and shop outside.
You are strongly encouraged to stay on site, but I found that a bit oppressive after a while. Once you've been to the pool twice a day for 4 days straight, and rented the bikes, you've done it all. We had to escape and go to a little Dutch town for a bit of a break.
Also, it was full of Belgians and they are a sour puss bunch. Nobody was willing to have a chat while the kids played together, they all just sat there with a face like a smacked ass.
I guess it depends on your tolerance for being treated like you are going to a summer camp, but without making any friends.
