Yes, it's the "Ford/Schulman" room block, which is at the location of the wedding ceremony & reception (The Westin Chicago North Shore in Wheeling).
Your invitation should have your # of seats reserved on it. Children of all ages are welcome, so if you have the seat reserved, it's up to you if you want to bring your spouse, or your neighbor's kid that you sometimes babysit.
O'hare is a much closer airport to Wheeling: 18 miles vs. 40. At the same time, it's all Chicago, so we promise you'll make it there. Midway's Orange Line takes you right into the heart of downtown.
Driving or taking a Lyft/Uber (or taxi) is going to be the most straight-forward and efficient way to get there, even in rush hour. From O'Hare, it'd be a 20-30 minute ride. Prefer public transportation? Catch the 270 Pace Bus (Milwaukee/Gale) Northbound to Milwaukee & Wolf, which leaves from Clark/Lake downtown. The bus stop is quite literally steps from the hotel. You could also take the Blue Line from either O'Hare or downtown to Jefferson Park, and grab the 270 there (recommended if you're traveling during rush hour).
It's Chicago in November!