If you go into Chicago. Its hour drive with traffic (at 5 even longer) and train outside base took about 1-1 1/2 depending on stops and delays. Plus you got watch schedule to get you back in time. When road back in on Sat there was one that left at 7:35 (and we pulled out at 7:40) and then next one wasnt till 11pm.  Even if you drive into Chicago learn bus routes because it can save you time and parking money ($18 to park most places).
Expect hour long wait for Sears Tower (unless you purchase tickets online).But was amazing view and Giordano's Famous Chicago pizza is across street. AMAZING but expect a 45min wait on pizza!
Navy Pier is cool with Bubba Gump restaraunt (bout 30min-hour wait) and the bay is beautiful but only ride for adults is the Ferris Wheel (40minute wait for us), and boat tours..thing to know though about Navy Pier that I didnt know is that there are two clubs there so its the Chicago nightlife on Fri and Sat evenings beginning at 6.
Tell you the best place was the museum park! You can park and walk to all of it..The Aquarium, Planetarium, and Field Museum plus it overlooks the bay (again beautiful) and there's little delis and cafes and Chicago dog stands with picnic areas to eat and just hang out.

Hope this helps any of you planning your weekend. Best thing is find somewhere to just sit and enjoy your sailor. He/She hasnt been allowed to talk and they are looking forward to telling you everything. Make you lists of questions because Zac loved us asking him all about everything and having the list will help because believe me you'll be starstruck for first hour or two :-)
Good luck to all your Sailors!  HOOYAH!!!

Proud Navy Mom,
Deb