I'm glad to see other ideas than St. Joe, MI, Wisconsin Dells, and Lake Geneva on this list! People from Chicago seem to think these are the only three places in existence outside their suburb and the City of Chicago!
I'm from MI, and have lived in the Chicago suburbs for 9 years now.
Grand Rapids is nice, so nice pick! You will like it.
For future trips....
A few years ago, we did a weekend trip to Milwaukee with the kids (ages 14, 10, and 8 at the time). We left the western Chicago suburbs Friday evening (if you start heading north on 294, which turns into 94, at around 6pm you are headed against the traffic, and by the time you hit 94 the majority of the traffic is over), stayed overnight near the Wisconsin border. Sat AM we headed north on 94 to the Jelly Belly outlet/warehouse and did a tour, then headed to Milwaukee and went to the Safehouse for dinner.* The next day we did a Sprecher's brewery tour, who are famous for their root beer and sodas as well as beer, so very kid-friendly! We had a ton of kids on our tour and they all loved the soda/root beer samples at the end. I can't remember where we stayed in Milwaukee, but it had a nice pool which was really all my kids wanted out of a hotel anyway. We were supposed to do a winter hike in the area too, but it started to snow really hard and we left for home earlier than we had planned on Sunday morning.
My kids say it was the most fun vacation they took. And we had even surprised them with a Disneyworld trip the fall before that! (seriously!!!)
Starved Rock is a fun day/overnight trip too, if you like the outdoors. It's near Utica, IL.
We have also gone down to the college towns for sports/football games when our favorite MI team is playing, if you are into that at all. Lacrosse and baseball are both in season right now.
On the west side of MI - Grand Rapids, Grand Haven, Luddington...Muskegon....all have great things to offer and are within a few hours' drive. We go there to visit two of my sisters who live in those areas, but mostly when we go "home", we got to the east side of the state where we are from. If you ever want to go east of Lansing, let me know and I can help! lol
Have fun!
*If you ever decide to go to Safehouse, DO NOT cheat and find out the secret code on the internet! Although I will say to get the most out of it, research it a *little* so that you don't walk right past the surprises. t's a James Bond/spy type of theme, and SOOO much fun!