I didn't go to Mommycon Chicago but pugz and I went to Mommycon KC last fall! Are you VIP? I got 90% of my swag through being a VIP.
For the mass giveaway session at the end sit in front if you can. A lot of giveaways are based on hand raising or first person to the stage. Read a bio of Jamie Grayson because a lot of questions are about him because he makes them up.
Jessica from TLB and January from BWF are super sweet.
They do not recommend strollers because it's pretty crowded. Babywear if you can.
The Museum of Science and Industry is my FAVORITE museum here, by far. The CTA tracker was a great suggestion; very accurate. I have an app called Transit Stop that might be easier than loading a website, if you have an iPhone. I also suck at city restaurant recs since I rarely eat downtown (unless you count grabbing takeout and bringing it to my desk!) - however, since you're staying in Rosemont the new outlet mall is pretty nice! Sales tax is still around a billion percent in Cook County, though, so it may not interest you. Have fun!