I would guess that the swapping of SD cards would work well. I also thought of two alternatives:

1) You could use the same SD card/library for everyone, but they could bring their own jump drive to save files onto. I find these drives a little easier than the SD cards, and, this way, if a particular document were needed for annotation/reading/whatever by everyone, they could all have access to it. If desired, they could also look at each others' notes and annotations.
2) You might be able to download a file manager that would allow you to upload to dropbox. Each person could have their own folder.

Hope that helps.