Sorry Nappy I have just got your message!
For my tuppence worth :
We go along the coast a lot. Pontins in Prestatyn looks like a prison camp from the outside, have never stayed there. I would think you would be better off in a b&b or something. The Haven site at Presthaven sands is supposed to be nice a#but again theis is hearsay as I have not stayed there myself.
The beaches you come to on the north wales coast are as follows:
Talacre. Loads of holiday parks. Just at the end of the esturary so very muddy beach. Lovely sand dunes quite a distance to the water. Fine for sandcastles not for paddling.
Prestatyn sandy but still a little muddy. Very seasidy feel to it. Nice play parks
Rhyl think tacky Blackpool
Kinmel Bay Towyn again very like Rhyl...
Abegele stoney beach. However you can drive onto it which my kids think is fun!
Colwyn Bay Great fish and chips boats in the little harbour. Not much in way of sandy beaches IIRC large prom all along good for cycling (this goes from prestatyn all along the coast)
Rhis/colwyn tend to be full of old people lol
LLandudno great as above. Sanyish beaches shops donkey rides punch and judy (scares my kids) downside of this is more for them to pester you to pay for! However this is where I go most for day trips as they rarely get bored and somewhere to go if it rains.
Anglesey has amazingly clean beaches - we camp here a lot
Lleyn penninsular, haven't been for a while but was lovely on the few times I did go.
Hope this helps and is not too late! Ask away and q's. For what it's worth we regularly go to Talace for a couple of hours and my kids who are nearly 6 4 and 1 are perfectly happy and we are not constantly pestered to go in the water because it's too far out. (every cloud has a siver lining and all that!)