John,
Three Cliffs Bay is a lovely site. The view from the campsite is excellent and the beach is probably the best beach we've seen in South Wales (so far). We were there with our 3 children and our friends were there with their children. It was a very quiet site and we appeared to be the only ones with children in the caravan area.
We have an 8m TA and I found the access road to the site very tight and once onsite the hedged lane to the caravan area was extremely tight - both wing mirrors touching the hedges!
The walk to and from the beach was very steep and is probably the only reason we would not go there again (until the children are older). The campsite path to the beach was more suitable for mountain goats! We took the longer route back which was pretty hard going with three little ones and body boards etc.
Cheers.