Held in Roald Dahl Plass, in Cardiff Bay, a fair walk from Cardiff Camping And Caravan Park http://www.cardiffcaravanpark.co.uk/ but an easy bus trip or for the more adventurous you can take the Water Taxi from Bute Park to Memaid Quay or hire bicycles from Pedal Power located in the caravan park.
I would not recommend driving a large camper down to the Bay, parking is in multi-storey car parks or there are limited on street parking spaces although Cardiff Council can be quite forward thinking and often open up a bit of awaiting development land to motor homes.
Cardiff Bay, you can take boat trips on the Bay.
Welsh Assembly Building.
Cardiff Bay Cycle Route or Walk. Takes you around the Bay (10 kms) via the docks area, Cardiff Barrage, Penarth Marina, White Water Canoe Centre http://www.ciww.com/, Sports Village, Memaid Quay http://www.mermaidquay.co.uk/ good for a wide variety of restaurants, coffee shops and one or two bars.