Brown paper lunch bags. Plain white card envelopes. Washi tape. Ribbon. Baker's Twine. Decorate to your hearts content. Though, I do discourage you from staying up until 2 to finish this step.
Slip in a tiny scrap of paper with a fun family activity and two small treats - which may or may not be leftover Halloween candy. And by may or may not I mean definitely was. I was going for on-hand here, remember? I also slipped in a few non-sugary treats like some super balls and sticky hands.
Maybe next year I'll make something crazy awesome. I'm saving the bags as we open them as a backup though.
It's only December 5th. You still have time. Especially if you go this route.