Since you're in boston, I'd do a check on the front bleed nipples regardless. Make sure the rubber caps are in place, etc.

If the fronts weren't touched and you kept the reservoir at least partially full, then you can't have gotten air in the lines for the front so no need to bleed them for air.

If, while replacing the rear calipers and refilling and bleeding those lines, you let the fluid drop then yes, you do need to bleed the front lines because you may have let air get into them from the top.