Our Nephew is intellectually disabled, he is 12 and has the mental capacity of a 2-3 yo. It is hard to buy for him as he has so many toys at his current level. We tend to alternate between clothes and toys. Even his parents (DHs Brother and SIL) struggle to find new things for presents

How about a bubble machine?
Push Along Cars?
Wooden Train Set (IKEA have a good one)
Blackboard?
Tickets for the Zoo/Family Day out etc