I'm in a similar boat. What is on the idea list so far is Perplexus Warp since he has all the other Perplexus mazes, a card game, Skip Bo, and an adult size sleeping bag. I'm sure I'll find another game or two since my tween is into games.
I'm also looking for a very soft hoodie or sweatshirt.
Stocking stuffer ideas: Silly string, magnetic thinking putty, nail clippers (they keep getting lost so each child is getting one!), deodorant, tic tacs, and favorite gum.