Close friends having their wedding same month as ours, what is the etiquette?

Have your wedding when it suits you. Once you know the date, tell (not ask) the other couple. Once the other couple set a date then your fiance can give his final yes or no to officiating, and there's nothing wrong with bailing out since they've moved the date. I'm sure officiating a wedding is a great privilege, but you don't move your wedding for it. And if his clique-ish friends don't want to go to two weddings in a month then they're not great friends anyway, so certainly don't move your wedding to suit them.