They'll probably work. The Library database is around 50MB, depending on your configurations and the number of V-Scanners used, you'd probably be ok there too. The main issue would be if you wanted to do a lot of audio recording.
They will work if you format them with the software...However...just a thought....You can get a new class 10 (the latest / fastest speed) card 4gb in size for about $10. That's what I did.