Afan works quite well for me with family beach holidays to Porthcawl – not quite on the doorstep, but not far away either.

Alternatively Minehead has riding right from the beach and not far onto Exmoor.

pont sgethin and barmouth;
aberdyfi and the dyfi trails

could go on and on

Aberdovey, Fairbourne, Barmouth, all have very nice beaches, close to a few trail centres and Cader Idris is always worth a climb.

dorset campsites – toms field @ langton matravers nr swanage. loads of riding, coast, beaches, pubs. walk to dancing ledge or the square and compass at worth matravers.

if thats full theres one up the road or a nice old farm campsite at harmans cross.

Or Burnbake – can cycle to Studland on traffic free good trails (apart from a 5 minute time trial on the ferry road, much to the tag a long passengers approval.. choruses of Shut Up Legs from the back)