Actually, if you go to Glenview, go to the busy ice cream shop west of the tracks.
gotta ask... where can I find the best ice cream and/or frozen custard shop in Chicago? (or as far as O'Hare?)
Thanks!
My favorites are Scooter's and Lickity Split, of the local custard places I've tried that aren't a chain(namely Culver's and Andy's Frozen Custard, though those 2 aren't bad for chains). There's no shortage of places that make good ice cream(and gelato as well), such as Chocolate Shoppe(near the Edgebrook Metra station), Paciugo(3 Chicago locations, they are a chain but decent), Black Dog Gelato. For the suburbs(probably will forget some, don't hate me if I miss some), I did like Glenview Dairy Bar, Plush Horse(Palos Park? forget the one it's in, but near one of the Southwest Service Metra stops), Dairy Star(Lincolnwood), Brown Cow(Forest Park), Homer's(Kenilworth), and Petersen's(Oak Park).
Feel bad my membership signing up process to create an account on this board today took a little long and that this reply to the OP is a little too late to help him/her out, but I was going to suggest a Metra trip over doing one on South Shore, Amtrak Hiawatha, or any Amtrak Illinois trains. Not that the latter 3 are bad(I like any of those latter 3 too), just you'd have more time to enjoy yourself if you did a Metra trip. Since honestly he/she would've had very little time in Milwaukee, unless the OP would've been happy with only a 4:44pm-5:45pm(1 hour, 1 minute IF it was on time) layover in Milwaukee. Where in that case, I would've suggested going inside the Milwaukee Public Market(this'd probably have been the best idea to do with that short of a layover, and there are places inside there where OP could've gotten a bite to eat), or finding somewhere nearby to eat or drink in the Historic 3rd Ward neighborhood. Which is only a short walk east, on Saint Paul Avenue.
I was going to suggest the 2:45pm Metra train(if you didn't mind leaving a little early, and arriving at Joliet at 3:50pm) on the Heritage Corridor line out of Union Station, and then coming back at 6:15pm from Joliet with a 7:42pm arrival at LaSalle St. station. You'd have to Divvy bike or Uber/taxi your way back to Union Station if you did that, keep in mind. Other ideas I like are taking the BNSF to Aurora, Union Pacific West line to Geneva(nice downtown, and the park along the Fox River is worth a look), or(in lieu of the idea of going to Joliet) taking the Rock Island train to Blue Island-Vermont St(which serves their historic downtown) and back. I'm not sure why Blue Island always seems to be underrated when people talk about destinations off of Metra, but I love how historic that town is. Very nice, and there are also good places one can eat at or have a beer at as well(i.e. Rock Island Public House, Blue Island Brewing Company, Maple Tree Inn to name examples).
Whatever you decided, I hope you had a good trip taking the(probably a Metra) train to somewhere.