Go for it.
If he can survive a road trip, he can survive a train trip. Keep in mind that Amtrak has several stops in the Detroit area (Dearborn, Detroit, Birmingham, Royal Oak), so find the one that's most convenient to you.
If this is going to be a one-day affair, the best bet is to take train 351, which leaves the Detroit area around 7 AM (exact time depends on where you board), and gets to Chicago just past noon (if on time, though sometimes there can be delays enroute). Train 354 leaves Chicago around 6 PM, and gets to the Detroit area around midnight.
If you're going to spend the night in Chicago, you have other options, including two later westbound trains and two earlier eastbound trains.
Make sure you bring something to do (books, games, etc.).
The trains will have a food service car, which can be a bit on the pricey side ($1.50 for a can of Pepsi, but what do you expect for a "captive" environment). On the other hand, you can spend an extra $9 per ticket and upgrade to business class, and you'll get a coupon good for some free stuff in the lounge.
Right now I can't think of much else. Since this isn't a long-distance trip, there's not much advice to give.