We went to St Ives Bay holiday park a couple of years ago. It was lovely. The caravans are in the sand dunes with great views over the bay and you could walk to a great surfing beach with lifeguards. From what I remember the pool was fine. The clubhouse was popular (but not really our thing) but the good thing was that we could sit and watch dsd in the playground outside.
I've been to Sandy balls (yeh great name) nd really enjoyed it. But I reckon the best place I've been to is Sandown Park. It's great for kids. It has 2 outside pools, one with a man-made little beach. One indoor pool. All the usual entertainment as well as crazy golf. But the one thing thtatI really liked was the fact that every caravan was enclosed by its own hedge, so it felt like you had your own little garden.
Also had a drive through Hoseasons in Hayle (near to St Ives Bay Holiday Park) and agree that it looked awful! Would not touch it with a barge pole, and the beach didn't look to special there either - avoid!