Suggested itinerary wanted for Bath to South Wales....

We decided this year to focus on Bath (for the third time) and then
travelling over to South Wales this year. We will be driving from
London to Bath where we plan to stay for 3 nights. after that, we plan
to drive to Southern Wales since we were in North Wales last year.

There are 4 of us (mom, dad, 17 and 15 year olds).

We plan to drive so will have a car.

We like museums and especially castles (ruins or not) and abbeys.

Anyone have a suggested itinerary for leaving from Bath towards south
Wales for 6 days (places to spend the night, castles to see each day,
etc.)?

when returning from Wales towards London, a suggested route or return
via Bath?

any recommendations on castle tours in a suggested itinerary as well
as recommended B&Bs is greatly appreciated.

steve