G.D.
I don't think a potluck is rude at all. In fact, I'm with mom2many-I don't like to come empty handed.
Why don't you put a spin on tradition and invite them for a lunch get together? You could do easier food (like a sub, a deli meat tray, cold salads etc). The kids could all run around and shre their excitement and all five families will be able to get them in bed without a hitch.
Only 9 days to decide and invite!