I hate to inform you that Clem and Ursie's is no longer, they closed up rather quickly last month or so. We tried to eat there at Halloween and were greatly disappointed.
I can make a list of places that we like that may or may not be open while you are there:
Ciro and Sal's - good Italian and a long history
The Squealing Pig, or "The Pig" - decent bar food, and a good fish and chips, local, "unfabulous" crowd, very laid back.
The Mews - great for apps and drinks
Bayside Betsy's - most of our friends love this place, or at least use it as their fall back choice. I have to say we are not quite so impressed.
Ross's Grill at Whaler's Wharf - We have had some great meals there, and some average meals there, great view, and decent drinks.
Saddly, Chester, the best restaurant between NYC and Boston is now defunct, part of my soul died the day they closed.
My last recommendation is to eat frozen pizza and warm soda before you eat at the Lobster Pot.
Easy on the Lobster Pot, especially in the off season. We ate there in a snowstorm and had the best, freshest salmon I have ever eaten. Mews is great but eat in the cafe. We eat a lot at Fanizzi's and enjoy the atmosphere in front and the food. I do not like Ross' Grille, I have had bad experiences with their seating and would rather eat the take out box than to recommend anyone eating there. Front St is a great, intimate dinner setting with good food and we are doing more at Jimmy's up on the west end.....I do not miss Chester as much as garden does but there is still the Red Inn.....
Ross's can be loud. Sorry about the bad experiences there, that's so unfortunate. We've had good and not so good meals there.
Fanizzi's is one of our favorite's, it has always been a constant of good fresh food, beautiful views, and friendly, but not in-your-face service.
Many people diss Napi's, but we like it, especially in the off-season. Been going there for over 25 years and haven't had any big issues with the place.
Agree, The Mews upstairs, not down for apps and a martini... Pingle shakes a mean one!