North Pond, for the lovely setting as well as the food. This assumes your elderly mom can walk a distance of roughly a block or so into the middle of the park where the restaurant is located.
Cafe des Architectes, in the Sofitel, is another excellent choice, with the best contemporary American food in the city, IMHO.
If you happen to be staying in the Loop,
Atwood Cafe is another good choice.
All of the above are not particularly noisy.
Don't rule out
Topolobampo until you've actually checked on reservations. Like the others listed here, they're on
Opentable so with a few clicks of the keyboard, you can check availability on these and hundreds of others at the same time.