I think they'd be okay outside. Keep in mind that potted plants are exposed to temperatures about 2 zones colder than those that are sheltered down in the ground. So since you're in Zone 7, you should do okay with Zone 5 plants in pots. Peonies are hardy down to Z2 and hostas to Z4. Just to be safe, you could put the pots in a spot where they are sheltered from wind and maybe insulate them a bit.

Keep them out of the sun as well, especially if they are dark containers. This will help prevent the freeze-thaw cycles.

tj