We considered Kernow, last year, but in the end went to pembrokshire with our (then) 14 month old last year – stayed near saundersfoot, nr Tenby. Beaches were good, but weather wasnt, meaning we pretty much had them to ourselves meaning lots of running round and general rioutus times for the kid.
There were plenty of other things to do – farm up the road for kids, which was pretty good. Did a walk through Bosherton Lakes to the sandy beach there – which was great (although, not great with a buggy, it was managable). Planning on going back this summer.
Initially looked at Bluestone, balked at the prices and found ourselves a decent little cottage for 1/3 of the price of what is essentially a middle class butlins