Well, if you feed them tomorrow(kind of a light feeding) then do a big water change. Sunday when you get home do another big water change and feed again. That would really only be 4 days with no food. That's probably going to be fine. Your gonna come home to reall, really hungry rays...but they should be no worse for the wear. It is a lot harder on young rays than it is on adults, but I think 4 days they will be ok.