I'm really glad the Buffalo suggestion looks like it could work out for you
I think 2 nights in/near Niagara will be plenty. We only had one night in Niagara, flew in late afternoon and flew out early evening the next day. We did the Maid of the Mist, the attractions/movie at the visitor centre, ate lunch, wandered around the park and then had time to do some shopping in the afternoon before we drove back to Buffalo airport for our 6pm flight to Orlando.
Whatever you do be prepared with a change of clothes ( or be prepared to go back to your hotel to change) after the Maid of the Mist. Even with the ponchos on we got very, very wet!
In Boston, we ate at Cheers near Fanueil Hall - the place was packed as it was Columbus Day weekend but we enjoyed it. I have a couple of cute photos of me with Norm and Frasier

( Life size cardboard cut-outs)
I'd love to go back to Boston, hope you enjoy it!
Andona