Howdy. I've actually thought about this topic because for a while it looked like I might be getting the same job and setting up a similar studio.
My initial thoughts:
Wireless transmission of video doesn't sound like a good idea to me. It might add cost but it could also increase the chances of something going wrong. There are several ways to get a video signal via wires from a DSLR to a switcher. One of them being HDMI to SDI converter boxes. We've used this method at my church and it works fine, even with long (100'+) SDI cables.
A Mac with Final Cut Studio 7 has worked great for me for recording. The only software-based switcher I've used was 15 years ago in college. But the little research I've done since then hasn't convinced me that a physical switcher wouldn't be better because you're going to need some sort of interface to input all the different sources anyway. I don't know though.
You might also consider buying HD video cameras instead of DSLRs. There are advantages to both. A video camera might be easier to control in a live studio setting (and would allow for hand control zooming/focusing on the fly), but DSLRs would provide a different type of experience that might be useful later, depending on their career paths. There are some inexpensive video cameras out there with smaller chips that are made for that sort of application. Might be worth considering.
Anyways just my two cents. Have a nice day!
Creative Services Producer
WSLS, Roanoke VA