Will be staying near Ammanford on holiday this summer. Our kids (age 5-10) mostly like woods and hills but also we will want to go to the beach a couple times.
Have one kid with autism prone to running off and a place with cliffs would be too stressful unless it's just going down a set of steps to get to the beach. None of the kids are particularly fussed about going in the water. Somewhere not too crowded, has some rocks etc as well as sand, has toilets and maybe someone selling icecreams? Some friends recommended the Pembrokeshire coast rather than Carmarthen Bay places like Tenby, but not sure how long it would take to drive (one child throws up in cars...)
Will be going to Carreg Cennen and Dinefwr, but are there other places in the Brecon Beacons National Park you'd recommend for picnics and walking?