Oooh a trip to Chicago..how fun!
My favorite hotel is the Fairmont...very beautiful, very romantic, with fantastic staff. It's around $200/night, but they always have specials http://www.fairmont.com
It's right near Millennium Park and walking distance to all the Loop attractions.
Congress Hotel..a Chicago classic, but smaller and not as ornate..maybe $100/night.
Four Seasons..good if you are a shopper, right near Water Tower Place. The swankiest of the swanky.
Palmer House Hilton..my #2 pick..very beautiful..have stayed here and at the "other" Hilton for some conferences.
My favorite place in the area is Blind Faith, but it's up in Evanston, which is quite a haul if you're staying downtown.
There's a place called Opera, which I haven't been to, but that is rumoured to be excellent, that has a vegan menu and is pretty fancy schmancy. Their address is: 1301 s wabash ave. Phone: 312.461.0161
Some fun things to do:
*walk along the water/people watch at Oak Street Beach
*visit the Art Institute
*see a play...there are many to choose from
*catch some live music at one of the many places on North Clark St.
*walk around Millennium Park
*visit the sculpture gardens at Garfield Park Conservatory
*talk a walking history tour in Chicago or nearby Oak Park
My list is longer, but I'll quit before I bore you to tears.