Well, that depends on if the rally or the local beach has any firearms ordinances in effect. If you have a safe enough backstop, the albums could be stood up on a typical wooden frame. If you are facing out over open water, it might be reasonable to launch them with a clay launcher. I suspect CDs would fare better going through a clay launcher. Some nice #7 shot would do the trick.
CDs have to be hit broadside by a shotgun blast to have much effect, and launching them on a stable flight path where the flat side faces the shooter is difficult.