I really like the Blackstone Hotel on Michigan Avenue across from the park. Restored and beautiful. If you want to stay at Magnificant Mile, the Renaissance or Chicago Marriott Magnificent Mile is close and very nice. Good restaurant next door to Renaissance (Catch (something). If you're not using points and have to pay, register your Mom if she's a senior citizen - better rate. If Wicked is still playing, it's definitely worth seeing. Your mom would probably like Jersey Boys. The double-decker bus tour is worth it. If you fly into O'Hare, you can take the elevated train (blue line) to the Jackson Street stop. The train station is not a long walk from United - if you fly in on another airline, take the airport train to United. It's $2 per person, safe, and easy. Plus kids like it. The Jackson Street stop has an elevator, so will be easier on your mom - and with baggage. Take a cab to your hotel, but you are now downtown so it shouldn't be over $10. Good restaurants: Rainforest for kids, for good steak PrimeHouse or Keefers. For prime rib, Lawry's. Joe's Crab (Magnificent Mile) is very good. LOADS of good restaurants but expect to pay about $34 each - plus drinks. For others, if you go to Chicago, the American Girl (doll) is a must, but make reservations in advance for lunch and be prepared to spend some $$$.
If you're looking a hotel that will treat you as a King or Queen in Chicago try the Renissance on Wacker Drive or the Mag Mile Marriott. I tried The Blackstone three weeks ago and it was the worst experience I have had with a Marriott brand. The room was dirty, we found used wine glasses in the room. We asked for extra towels, and over a third of them had hair and makeup stains on them. As a gold member we asked about covering our breakfast since the lounge was closed. Well the Blackstone agreed until it was time to checkout. We sent 30 minutes of our day fighting with them over their broken promise. There are so many amazing properties in Chicago, there is no need to pay Renissance prices for Blackstone service.