That's nice of you to help out the little guys.
I'm not sure about the care that they need, but I am sure that if you use what you have until you know how big of an area they will need, then they will be fine.
The only thing I know about them is to make sure they can't get out. My parents used to rescue sick animals, like baby birds, squirrels, rabbits, mice, whatever came along our yard, and it was hard to let them go once they got better. But because we have house pets, we had to be super careful, because animals from the outside can make your indoor pets very sick, only because mice tend to 'break into' any food you have, and you don't know the common diseases that the mice are carrying.
But, I'm sure you already are being careful! It's sweet of you to think about the poor little mice, because a lot of people wouldn't, just because they are wild. Maybe you could call your local vet, and s/he would know when they would be well enough to release into the wild again, without having to take them in for an expensive visit.
This is kind of off-topic, but I remember when we took in a baby squirrel that was injured, and he was so little that he had to eat from a bottle. So we called the nearest petstore to see if they had little any of that kitten formula, because that would be good nourishment, and they said that one employee had a cat that just had kittens, and the cat and kittens were at the store so the employee could watch her or something, and so they let the squirrel nurse off of the cat. It was so cute! And the cat didn't even care!
Anyway, let me know what happens to the little guys!
~~Kelly