I agree with the others - hotels outside Boston are (a lot) cheaper.
Be careful where you DO stay though. Not all neighborhoods are... well.... nice. The hotels may be stunning, but not really the sort of place you want the kids wandering around.
Where you have the kids, and if you are willing to stay 10 miles out of "downtown" you can get places with a kitchenette or even a full kitchen for less than the price of a Boston room.
Enjoy your trip!
Complete opposites - Elvis wants someplace tropical for his birthday and I want Alaska for mine!