Thanks to all, especially kate@50, for suggestions. We were just not up for any kind of road trip, so we went to Intrigue in the Boston Harbor Hotel. We got to sit outside and admire the harbor, their rather picturesque gazebo thing, and an almost-full moon. That was exactly what was required, and we had a very pleasant evening (but read on).
The entrance is right off the lobby of the BHH, and the dining room, with chintz armchairs and round tables, feels like a continuation of the lobby. Outside was much better, with canvas cafe umbrellas and glass tables.
The food was okay. It's quite inexpensive for an ambitious restaurant--cheapest entree was $13.50 (a caramelized onion pizza) and most expensive was $24.50 (lobster). But they were all small, what I would think of as demure lunch portions (the lobster was about half a lobster's worth of de-shelled claw meat, no tail meat, arranged on a plate), and, curiously, none of them came with more than one very basic accompaniment: a small corn pudding for the lobster, a romaine salad for the redfish special. I don't usually expect to get EXACTLY what it says on the menu and not a drizzle of sauce more, but there it was. Nothing was very imaginatively or detailed-ly prepared. The grilled redfish tasted more like charcoal than fish.
Also, despite the moderately priced entrees, there were very few, if any (I can't remember) bottles of wine under $40, and the wines by the glass were $9 and $10. However, the wine we had, an Alsatian pinot blanc, the cheapest bottle on the list, was thoughtfully chosen, crisp and dry with an interesting, bright-not-sweet apple finish.
I've never been to Meritage, which supposedly shares a kitchen with Intrigue, but I would expect it to be much better. Maybe it shares the same wine guy, but not the same cooking crew?
The service was fine and swift, but they did bring us regular coffee instead of the requested decaf (as we concluded when lying in bed wired at 1am).
So, in all, very nice atmosphere on the deck, decent food, and not a big investment. I'd take any non-foodie out-of-towners there again, but I wouldn't go back for myself or with sophisticated eaters.