I like the Shee-Atika Lodge for seafood (halibut and chips) and there are a couple of very colorful bars right on the main street in Sitka to enjoy an adult beverage at. Sitka is not very large and you can tour it in just a couple of hours.
There is a resturant right at the end of the street that the tenders drop you off at that had OUTSTANDING clam chowder and had a beer garden out front. Sorry I don't have the name, but if you ask one of the locals, they will point it out to you. It might even be the Shee-Atika Lodge that Tom mentioned.
I agree with Tom the Shee-Atika Lodge downtown is a nice place to sit and enjoy a seafood lunch. You can order one of Alaska Brewery beers there too. The Bayview Resturant on the second floor of the McDonald Trading Co. Building also has a good seafood lunch menu and your choice of alaska (and other) beers.
I recommend seeing the Rapter Center while you are visiting Sitka. This is a good spot to see various birds including the bald eagle up close.
And if you are talking things to do/see in Stika, if you turn right at the end of the road the dock is on and walk along the harbour, at the end of the park (right past the tennis courts), there is a sea life "petting zoo" where you can look at and touch/hold various sea creatures... star fish, sea cucmubers etc... It was free! (They take donations) and had aquariums etc...
It was great for the kids to get up close to the sea life and get some good education info too.