The summers in Boston are amazing. I'm affraid you just moved in the wrong year. I'd rather that weather to the humidity of New Orleans anyday, though.
If he didn't like Buddha's Delight, then I can't really imagine him liking any other vegan restaurant. The Seventh Day Adventists run a restaurant chain called Country Life, and they have more American style vegetarian meals (entirely vegan). They have things like tofu scramble, waffles, homefries, caseroles, etc.
I met spud at the Country Life in London and it was fantastic. Funny thing is that I never went to the one in Boston! I know it has funny hours, so I'd look at them online before you go. It's all you can eat buffet.
I just found the hours -
200 High Street, Boston, MA 02110
Lunch: 11:30am-3:00pm Mon-Fri
Dinner: 5:00pm-8:00pm Sun, Tues, Wed, Thurs
Sunday Brunch: 10:00am-3:00pm