Navy Pier & North Pier (just west of Navy Pier) are a great place to kill an afternoon. You should find a copy of the Reader there; check the music secton to see who's appearing in town.
The Cubs are on the road, but the Wrigleyville area (Belmont & Halsted, roughly) does have a lot of restaurants and shops.
Go to the Lincoln Park zoo; it's free and fun. Next to it is the conservatory, which has beautiful flora (check out the orchid room). Walk west of the zoo on Fullerton toward Lincoln Avenue; lots of nice architecture. You'll pass Clark Street; there are many nice stores, bars, restaurants & used music stores to the north on Clark. Lots of cool stuff like that on Lincoln Avenue, too.
Places to see music: The Abbey Pub, the Old Towne School (sometimes, but not always), B.L.U.E.S, Rosa's (for real blues), Fitzgeralds (great variety, high quality. You'll need to take a cab to most of the music places mentioned. There are some good local bars with music and comedy on North Halsted, and in the area around Belmont and Clark.
Most of what I've mentioned is near the lake on the North Side; there are other places in other beautiful neighborhoods, but they can be difficult to navigate into and out of without a guide. If you see something you want to do in the Reader's Guide in the Reader (if you aren't familiar with the Reader, it is a free newspaper available in most bars and a lot of stores), call first, ask directions. Give them your street location, and if you can't walk it, take a cab.
This is going to be a great weekend to be in the City. I'm tied up with "family affairs" or I'd join you. Have fun!