North or South?
South - Three Cliffs, Rhossili, Barafundle, Broadhaven South, Cardiff, St Fagans, Manor House Zoo, Folly Farm if you have toddlers/young children, Colby Woodland Garden, Dinefwr, Castell Coch, Cardigan, Penbryn, Elan Valley. Bluestone in Pembrokeshire would be a good base. Near there my favourite places to eat would be Ultracomeida in Narberth or Caffi Mor at Freshwater West. On Gower head to Cwm Ivy cafe or Three Cliffs Coffee Shop/Y Clogwyn. Plus an ice cream from Verdi’s! In Cardigan Pizza Tipi is good fun. Near Dinefwr in Llandeilo you couldn’t go without getting cake or ice cream from Heavenly.
North - Llyn Padarn, Llyn Idwal, Beddgelert, Zipworld Fforest, Beaumaris, Parys Mountain, Newborough Warren, Plas Newydd, Betws y Coed, The Welsh Mountain Railway.
Any of the National Museum sites are worth a look and entry is free.