So, we just got back from our week long trip thru the islands. Kelly's Island is a quiet place but does get a little more "hop" on the weekends. Try Seaway dock's down there. They have fuel (all kinds), a small store, showers and laundry, and very nice harbor. It's a little farther out of town but only a 5 - 10 min. walk. The island itself has some cool things to see. Check out the ice grooves, they're kinda groovey.

Middle Bass is indeed a quiet place. The winery is not open but if your into history its kinda cool to look at. Check out JF Walleye's. They have great food and a nice area outside with a wade pool that is really nice after a hot day. Just be patient as the service is REALLY slow. If you want to take the boat out to Vermillion there is a VERY nice French restaurant but you do need a dinner jacket. Its one of those kind of places. We had a blast and would suggest it to anyone.
The entire week was an awesome experience. We like to get a golf cart and run around the island and stop everywhere we can. My suggestion is to start at Joe's (Beer is Food, Eat at Joe's). See if Ally is around and find out when she is singing. She's got a great voice and is usually found at the Tiki Bar. After that, depending on when and how much you drink you can hit the Round House, then Frosty's, then down to the boardwalk. You will be able to spend hours shopping and drinking and eating.
Do call ahead and reserve yourself a spot though. Slips and dockage fill up REAL fast.
HTH