Congrats on your almost new babies
! How exciting.
I wouldn't be surprised if they only used one crate together, at first. Nothing wrong w/ that. It sounds like you have a nice size area for them to have as their own, and I'm glad you won't be locking them in their crates.
Be very careful on the spay thing...you should be okay as long as the male gets neutered before the female goes into heat. Btw, you usually want to spay the female before her 1st heat...so waiting til she is 1 may not be feasible...just fyi.