the 10 gallon set up normally is fine, Peter. They are really small and their is plenty of height in a 10 gallon that is set up as its supposed to be. Its just temporary. You could keep them in there forever though and they'd be fine.
They'd be fine in a 5.5 gallon!
Just make sure that they have a nice, warm, humid place to relax in when they arrive. Give them hiding places, food, and water, and let them settle in for a few days before you start messing with them too much. Avoid stressing them out.
Don't worry about standing that 10 gallon up on its side - just keep it simple. They'll be more than fine in there until your exoterra comes.