$100 may be an impossible dream.
What are you dates, how many people are in your group and how many beds do you need?. The private room for 3 at the hostel is running $189 night. It is near a subway and walkable to the Wilbur.
http://Http://bostonhostel.org
That said, somebody recently posted finding Marriott Copley Place for Thanksgiving @ $105 + tax and using dates of Nov 28 - Nov 30 for 1 adult and 2 kids I found the midtown for $96 per night plus tax on hotels.com. both these places ate near the SUBWAY but not all that close to the Wilbur
Prices will vary , so exact dates matter.