St Davids is small, quiet and a bit posh, with access to Ramsey Island via boat, Whitesands just north, Solva and the coastal path to the south. Lots of small villages and great beaches south from there, Maroles and St Brides.
In South Pembrokeshire, miles of beaches and coastal walks, from the kiss-me-quick of Tenby (still quiet and quaint) to the wilds of Freshwater West (Very wild). Stackpole and St Govens Head are great cliff top walks, although some is restricted access due to the MOD. Just check before making an plans.
Preseli Hills north of Narberth. MTB heaven. Singletrack issue 72.
I’ll dig out a few of the campsites and cottages we’ve used. Can’t recall the names ATM.
EDIT: Skomer Island via Martins Haven. As long as you like rabbits and puffins!