What sort of dinner are you looking for? Iggie's at Bolongo is a fun casual place. Mim's, next door, is great fish and seafood right on the water. It's not exactly half-way between town and Red Hook, but pretty close.

Very casual on the east end: Tap and Still or ITP
A bit more upscale: XO or Fish Tails

A bit more upscale in Frenchtown, near town: Hook, Line and Sinker, Bella Blu
Also near town: the restaurants of Yacht Haven Grande (Fresh and Grande Cru), Cafe Amalie (in Palm Passage).
Wonderful dining in town: Banana Tree Grille.