Idealy you need to give them as much space as possible as they like to roam. Although it does look big, the floor area is (as I'm sure you know) only 6' x 9'. This would be fine for hatchlings and young jeuveniles, but not for any bigger, well not imo anyway, sorry
If your torts are only tiny though it would be ok for a couple of years, but am I right in thinking one of yours is a Leopard?