you are INSANE!
first off... $3-4000!!!! get real! that is WAYYYY TOO MUCH!
second... CASH is EXPECTED! doesn't matter if it is your boss or not! the cash is used to help pay for the high cost of the wedding party. PLEASE follow customs and give CASH! if you really want to feel extravagant, then give $1000...BUT that is ENOUGH!!!!