I once gave my daughter a series of small presents, each in its own (very) small box, wrapped, and taped to the ceiling. Hey, you have to do something for the 12 days of Christmas. So, each morning, she would have to wander through the house, looking around on the ceiling for her present. “I have no idea how that got up there… Huh. Must be elves. Guess you’ll have to go get the ladder… again…”
This year, because she was away at school for her birthday, I mailed small boxes and money to each of her friends and had them mail a present to her. Turns out that each one of them, independently, got her a box of paper clips. Now, she has … enough paper clips.
I once gave someone a rug, wrapped up in a tube - fitted with a nose cone and fins to look like a rocket.
So, for the Magic The Gathering cards, I really would suggest either going with the “lots of presents delivered in a surreal way” or packaged together in a way that suggests that they are something else completely. … Maybe a robot or a rocket or a snow shovel. Some completely peculiar shape and size - that would utterly distract from the true contents.
Whatever you go with, the first thing you have to give him is a package of sleeves (assuming he uses sleeves…). Be really, really happy and excited that you gave him… sleeves. Yay? :dubious:
re: treasure hunt, have the sleeves each hold a clue to the location of a card.
Get a pr0n video with some sort of ridiculous cover, take the disc out, and put the Magic cards inside. Wrap the box with a little card that says, “Here’s something your mother and father thought you’d enjoy, sweetie!”
Get a big box of envelopes. Put the cards inside random envelopes and stick them back in the box. For maximum evil, make up some faker cards with jokes on them and add those in randomly as well. Close up the box and wrap it up nicely. Kick back and watch him sit and open and inspect every envelope.
Then spend 2017 watching out for Junior’s Revenge. 
What I’m doing for the kiddo this year: get a gift that is obvious from the shape of the wrapping, and is also something that they don’t want and have no use for. In my case, I’ll be wrapping a cast iron frying pan. Their real gift is then placed inside the pan, where it can’t be felt until the wrapping is removed. Then, torment them for weeks about what a great gift they’re getting, when it’s obviously a frying pan.
Leave them under the Christmas tree. Later, steal them from him and exit his life completely. #PRANK #SOCIALEXPERIMENT #ALMOSTDIED #COPSCALLED