I suspect that you'll receive a single 60GH/s unit.
I think the advice you've been given above about the Pi is good. You shouldn't need any extra cooling for the Pi. In general, don't try to power anything (like a WiFi adapter) from the Pi's onboard USB ports. Just use one of those ports to connect to a powered USB hub and everything should work fine.
There's a wealth of Pi information at
http://www.raspberrypi.org.
Random8