The $10 bit is the hardest.
I would do the 7th floor of Macy's. Double check their Saturday hours, but if you land at noon I think you will be fine there.
It has a very nice food court. The kiosks feature famous chefs so it's a way to grab something a bit different, that tastes really, really good.
Your Mom can maybe get a burger, no fries, for under $10 or something from the Frontera kiosk.
I would grab a bowl of Noodles from the Takashi stand.
Your sister is set for the shopping afterwards.
The sandwiches are great, but even the vegetarian sandwiches at Pastoral run around $10, and that doesn't include a cookie, chips, or soda.
Or you could go just west of the Loop (before you check in to your hotel) and eat at
Italian Superior Bakery, double check their Saturday hours.
You can be stuffed for well under $10 with pizza bread and a large salad.
Bongo Room is going to be hard, plus it's Mother's Day, to stay under $10 for even pancakes.
Perhaps, you should go non-traditional and head to Chinatown on Mother's day.
Moon Palace is clean and Americanized enough that my mum-in-law actually enjoys it. It's my husband's favorite ma-po tofu (if you eat pork) in the city.
I think you can forget Quartino's or Frontera Grill, and Hancock for drinks, with that $10 ceiling, unless your mum is like my mum-in-law and literally eats like a bird, then the $9 appetizer is all she will want. Does your mum get upset if you or your sister have a bill that's over $10 or just hers?
Were you willing to leave downtown or were you trying to do everything in the Loop to Michigan Avenue area?
Macy's Food Court
7th Floor of Macy's
State and Washington
Moon Palace
216 West Cermak Road
Chicago, IL 60616-1914
(312) 225-4081
Subway: Cermak-Chinatown
Italian Superior Bakery
933 S. Western Ave.
Chicago, IL 60612
312.733.5092
Hours: Tues. - Fri. 7 a.m. to 3 p.m.
Sat. - Sun. 7 a.m. to 1 p.m.
Lunch specials: 11 a.m. - 3 p.m.