I would, since hoppers really don't have alot to them. Small adult mice are at least a little more muscled. You'll likely see better growth on the bigger mice too.

As far as space, I think you'd do ok with 2 10-gallons or 2-3 tubs. I'd start out with 1.2 or 1.3 and see how that goes. You could always freeze half a litter every so often to save for your cornsnake and the other little one.

All you would need would be: bedding, food, water bottle, maybe some cardboard boxes/tubes for them to hide in and chew on. That's about it! Oh, and your cages and the mice themselves