In my opinion it should be "have". It doesn't matter that your message is to each of them individually rather than the whole group collectively; the difficulty here is that "everyone else" functions as a singular, so the ear is expecting it to be followed by "has". If you said "I hope that you, the interns and the other Opera Club members have..." then there would be no question that it should be "have".
It's interesting to look at the Google Book Search results:
138 on "you and everyone else have".
100 on "you and everyone else has".
So if you feel you should use "has" because it sounds better then it seems you're in good company.