One of my boys was really into Lego at that age. Does he like to build? The instructions are pretty basic (age appropriate sets) and he could even do them if his parents didn't want to sit with him to complete. Or just get him a tub of the blocks. Maybe not so great for taking on a trip or to a restaurant.
For that, what about a sudoko book or word find? My kids got some of those as gifts at that age and it would keep them occupied.
We had a game called Rat A Tat Cat that was super fun at that age. It's a memory/flip card game and we still play it now (much older) - but it was great fun. I am positive the parents could play it, or the uncle would. It's fast paced so not dull and super cute for kids - you can make it easier or harder depending on skill level. I don't know what company makes it but that company also made other award winning games for kids - we got a few after we received that one as a gift.
One of our relatives always gave us those every year.
Is he into puzzles? You can get cool 3D ones for kids where they build famous buildings or objects from movies etc. Depends what he's into.
Does he like books?
My mom always gave magazine subscriptions - national geographic may do one for kids, can't remember. The kids liked getting them in the mail every month.
That's the age where they start liking collections of things - does he have interests in anything? (other than electronics)? I'm with you. I am a fan of kites, and that sort of thing. Every kid has fun with one of those, and it gets parents active too.
Good luck :) Personally - my kids liked 'fun' toys that WE had to do with them (spending time with someone else was the fun part).