Cant help on the Clarach Bay point but as far as the Aberystwyth bit goes a popular place to stay in that area is Borth. Further north than Aberystwyth but not by much.
Haven used to have a caravan park there but they've sold it on to another group. Not sure who but its called Brynowen.
Quiete place, just across the road from the beach ( in fact the town is just one long road that runs along the beach really
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).
Plenty of places to visit - Aberystwyth, Devil's Bridge, Machynlleth (home of Owain Glyndwr's welsh parliament), Aberdovey., and the Centre for Alternative Technology which our kids loved. There is a small train station there if you didnt want to drive everywhere.
We've stayed there twice. My son was ill the first time and as a result we didnt get to half the places we wanted to visit so we went back another year