NPD positively thrive on negative comments of any-and I mean, ANY-kind. Some of them seek it. In their pov, it could be a type of fuel for them.
So don't beat yourself against a wall with zingers and stuff.
You know the expression "work smarter not harder"
First, I literally accept any offer of help to bring anything. *But be crafty*
You already had all the stuff for the team? GREAT! Thank him, ask him to bring some stuff you already bought. Bring everything with you in case he "forgets" but stash the stuff you asked him to double-buy under the seats so he doesn't see and accuse you of "you don't trust me to follow through"(you know how they are). Thank him because you were in such a rush!!! Money in your pocket, after school snacks for your kids for the next week or two.
Narc's are very stupid because their brains get fried from only thinking about themselves. Use that