Henry for museum is in Dearborn.
Warren dunes state park in far southwest michigan.... It's 5-10 minutes off the I-94 interstate....
I've always enjoyed stopping in New Buffalo, Michigan. It is a small beach town you'll reach the first stop into Michigan, a few miles off the highway. Redamak's (casual burger restaurant that's been around for ages - cash only, http://www.redamaks.com/) was a staple growing up, as was Oink's for ice cream (I believe may also be cash-only, http://oinksicecream.blogspot.com/). The town has several shops in its center and is an easy walk to the beach if you'd like a quick stop.
You didn't mention when you're traveling (months and days of the week). Please note the beach communities may shut down certain days of the week during their off-season. Redamak's is closed from mid-November to March 1st.
I just took a road trip to Ann Arbor this weekend, which is to the southwest of Dearborn. I'm situated about 40-45 minutes directly to the south of I94, but east of Chicago about the same length of driving time, so it's a wash timewise.
It took us a good 6 hours driving time each way - with about an hour lunch stop and not much for a couple of others (gas, produce) - going non-interstate, except for about an hour on I69 NB. On the way back, we went non-interstate all the way. We came up against several instances of slow moving traffic (several oversize loads with state police escorts, as well as just other escorts) on Friday and some major road construction projects, both of which you'll also probably have along the way.
Which way were you planning on going? I94? Toll road? U.S. #12 for a portion?*
And when are you going? Weekday? Weekend? Before the first weekend of September - or after?
First, you need to be aware that just driving straight through from Chicago to Dearborn is considered a whole day of driving in itself. As a rule of thumb, you should allot no more than three hours of driving per day, if you want to actually see anything else during the stops/detours. Please keep in mind that many websites don't give you "real time" figures which include delays due to traffic and/or construction. They are estimated and don't include those factors, so read the website carefully.
If you are taking U.S. #12, there is a major bridge construction project near Bronson (east of Coldwater),
with about a 45-minute detour. Further to the west, there is another road construction project in Saline which encompasses about 9-10 city blocks, where U.S. #12 is completely closed to eastbound traffic. However, the detour is very clearly marked and doesn't take very long, as long as traffic is moving and isn't backed up (such as at a rush hour).
Truthfully, didn't see any local license plates on the vehicles parked at Redamack's when I went by yesterday. Just a large bunch of out-of-area tourists. 3 p.m. local time and it was packed with them. Traffic was stop-n-go right in New Buffalo on #12 WB (mostly coming from the east) but dissipated quickly once you got about a mile west of the main intersection. Still, there was considerable traffic traveling at 55 mph on #12 WB, all the way up to the #212 bypass for Michigan City.
Sorry, I missed the editing window.
The OP needs to keep in mind that Chicago is on a different time zone than many places in northern Indiana (such as around South Bend and eastwards) and Michigan. They will already lose an hour traveling eastward without making any stops at all, if they have timing constraints.
My initial suggestions to the OP, without knowing all the details, would be for them to start out as early as possible in the day if on the weekend or right after the Chicago rush hour, if during the week.
I personally would concentrate on the driving without stops to get to the Dearborn area as soon as possible and then take a side trip. Possibly to the Henry Ford Museum and Greenfield Village.
Or perhaps if Ann Arbor is of interest, they are close enough to stop there. The University of Michigan Museum of Art (with a suggested donation of $10) has a fine collection. A couple of their current exhibits are Catherine Opie: 700 Nimes Road (photography of Elizabeth Taylor's residence and her personal effects) and The Connoisseur's Legacy: The Collection of Nesta and Walter Spink. Nesta Spink is considered an authority on the lithographic works of James McNeill Whistler.
Ann Arbor also has a fine selection of dining options. Next weekend is also their annual Art Festival (actually four art fairs rolled into one).Edited: 18 July 2016, 20:00
Sorry, I just saw this mistake...
"Further to the west, there is another road construction project in Saline which encompasses about 9-10 city blocks...:" That should be to the east.
BTW, Saline is to the south of Ann Arbor. I took Moon Road (which turned into State Street) straight north. It takes you right into the downtown area of Ann Arbor in less than 1/2 hour. The University of Michigan's main campus is right there.Edited: 18 July 2016, 21:17
Thanks for all this detailed information. We will be traveling on Aug 29, renting the car in the morning. So I think it will be at least 10 am before we get going. We prefer not taking the Interstates. So it seems there will be not enough times for more detours.