I'm curious why you use a * in the name of that chain - have they cyber bullies they set on you? ;-) We used THAT chain in Yorkshire last year and had a good time.
Anyway, back to helping you. We stayed in Hendra Holiday Park 2 years ago, fairly near Newquay. Quite happy with it, maybe a bit on the pricey side but Cornwall seems to be a bit dearer than elsewhere in UK. There is a charge for the pool which is a downside. Other than that the food and pubs are grand, play areas not bad. Our kids were younger than yours but really enjoyed the evening entertainment.
Have you a caravan or are you renting a mobile home? The campers toilets, showers etc were all good.
Could really recommend Cornwall - St Ives is fab, Crealy Adventure Park, Dairyland Farm is surprisingly good. Minack Theatre and beach near it are also great. So check our Hendra and then see if can do better on price. We broke the journey to there with a night at Mill Farm (or something like that), maybe an hour south of Bristol, near Bridgewater - let me know if you're interested and I can dig out the proper name. Lovely spot, indoor and outdoor pool, probably not near enough the coast for a full holiday but great for a stopover.
(& not to put you off Cornwall but great ferry prices to France on Celtic Link - same as cost of getting to UK)