Firstly, don't let your bunny and your rats meet - it's dangerous for both species, they could very easily injure each other.
Are you in America? If so, I'm guessing your measurements are inches, and so the area is about 6' x 3.5' which will give the same amount of space as most people's bathroom. That's fine if you make it interesting by giving them things to play on/in/with, but they won't be able to get a real run. If you could allow them into your main room then they would be able to run properly, but many owners aren't able to provide the space to do that anyway.
I think the critter nation cages are like our SRS, which has a shelf underneath and is on legs with wheels - this means that the rats can use all the floor space underneath the cage as well, so the cage doesn't impact on their play area. If you're taking the doors off the closet though, you'd need to consider how you'd be keeping the rats in.