It's just occurred to me that this might be an instancing problem. If you're not in the same "instance" of the system on FD's servers, you're both there, but kind of in parallel universes and won't see each other.
To be certain of being in the same instance, I think you have to use Group Play, which means you setup a group and invite others to join it. Then when you start the game, instead of Open or Solo Play, choose the middle, Group, option and you'll all be in the same instance of the system.
Rep +1 for the philanthropy. I'm gonna do something similar myself this weekend.
That would be hard to do since nobody actually stated they would show