When I was a kid, I was obsessed with turtles. I never got a chance to try box turtles though, but I had painted turtles and snappers as pets for a long time.
Box turtles are terrestrial. At that size they may be able to handle a small terrarium (not like a 10 gallon, larger, if you need to make one quick, get a large plastic container at walmart, I keep a plated lizard in two of those hooked together with a plastic pipe, it works well enough) It should have dirt on the bottom, and a water dish that they can get into/out of if they want to. The hardest thing should be getting it set up.
The most important thing right now is winter, either bring them in or let them go, if they are let go, they will need time to set up for hibernation. This will require finding a place and digging a burrow, so if they are going, they should go VERY SOON.
Here's a useful link:
http://www.marietta.edu/~mcshaffd/boxt/care.html
I always had my turtles under artificial lighting, so I never had any dormancy issues. With three turtles (snappers and painted), and at least 4 winters, I never lost one, or even had any get sick. Also, I would highly recomend growing at least some plants with them. Turtles, even carnivorous ones, will occasionally munch on plants, and the plants will keep the humidity slightly higher.
The only thing it doesn't mention is calcium supplements. They will almost certainly need some calcium supplementation, especially while young. Snails have a good amount of calcium - if you want to grow some, I have quite a few in an aquarium, I can send you more than enough to get started, I'm now overrun with them and ditchmoss, I have to keep throwing both out. Otherwise, calcium supplementation is a must, but you can get it at any pet store and shake food (crickets, mealworms) with it in a bag before feeding. Also, any kind of vertebrate (frogs, feeder guppies in the water dish) can provide some calcium.
Good luck, whatever you decide to do.