Weston-super-Mare is flat and has a long seafront and grand pier and lots of shops all on the level. There are quite a few B&Bs in the side streets leading to the beach (but need to check for a lift if Mum can't get upstairs). Also check for easy parking or not. There are also hotels along the seafront.
The sea is often so far out you can't see much of it 
but you do see lots of beach!
