I would be disappointed if I couldn't go with him, but I would be happy that he could go away with his buddies, as long as there were no females among them. I wouldn't make it about myself, it's your loved ones birthday. Let them have fun.
i myself would sit in the corner and whine and cry while beating my head on the wall, but what you should do is book you a trip to japan, as everyone knows them japanese women are hot