Unless you are going to supervise them 24/7 I wouldn't keep them together, same for the dogs.

We board dogs and rabbits. Rabbits are never put together and I would never dream of leaving any of the dogs together when they weren't supervised, if I go out they are seperated into different rooms all with locks or handles turned upside down to avoid them opening the doors.

You cannot take risks with other peoples pets. The fact that you are even considering this concerns me!