IMO the worst possible seating for adults and a round table basically deletes the use of 1/2 of the banquette Why not just get 4 chairs and a nice round table big enought to seat 6 in a pinch. with a couple of folding chairs to add that seating.

A pedestal table would be one of the best options when it comes to banquette seating. It will allow ease of getting in and out and you can add chairs on the other sides. See one of our designs below for some idea of what might work for you:

I prefer a rectangle, but then again I don't like corner banquettes.

The best type of table for a corner banquette configuration is a rectangular table