It really is hard to fault Four Seasons, in Chicago or anywhere else for that matter.
We booked one night here on the way back from a ski trip. We had two adjoining rooms, one for myself & my wife, and one for our two sons (aged 9 & 11).
On a previous trip to Four Seasons (in Las Vegas), on arrival the boys had been presented with gifts of cute little soft toys and so they were curious & looking forward to seeing what Chicago hospitality was like! Sure enough, the hospitality starts in the lobby, where there were cookies and hot chocolate for everyone while we checked in. And we we got up to the rooms, there was a game (Kids Pictionary) and more cookies & chocolate milkshake waiting for the boys in their room.
The rooms were very nice: great view over the Lake (we were on 41st floor, I think), extremely comfortable bed, big bathroom etc.
Breakfast excellent (didn't eat in the hotel for dinner so can't comment).
We also made extensive use of the spa facilities - decent pool, although maybe a few degrees colder than I would have liked, plus hot tub, steam room, sauna & massage facilities. For kids there were lots of floats, noodles etc to use in the pool which was nice.
Helpful concierge recommended an excellent steak restaurant (Rosebud) nearby for dinner. We had a really great evening and that added to the overall enjoyment of our stay.