you don't need an agenda really to have a big time in Chicago.
Wrigleyville itself has all kinds of atmosphere. Lots of bars and neighborhood type places to get food.
Ride the el train to the game. That is an experience by itself. And I assume there is still a great little sausage place right near the stairwell where you get off to go to Wrigley.
One bit of advice on going to the game. Watch where you sit in the park. The coldest baseball game I ever went to was on Memorial Day weekend at Wrigley. We sat in the shade on the third base side, it was so cold, but people in the bleachers were shirtless and nice and toasty. Sit down first base or in the bleachers. I always preferred the bleachers anyway, right field, row three.. Leave a lot of time for walking around the place too. They do not make ballparks like that anymore.