If you are set on keeping a tortoise, have you considered an Egyptian? (Testudo kleinmanni) Based on my reading, they appear to do well year-round indoors (can avoid the humidity) and grow to a maximum size of approx. 5 inches which speaks to your space considerations. (Although at least 4 square feet of habitat per animal seems needed since they like to forage). They do better away from cold climates, it seems, I don't know where you're located. I don't believe they hibernate but have been known to "estivate" if the conditions dictate. (Sleep through the hottest heat of the summer.)

Cheers.