As kids with ADHD sometimes have balance and hand eye co-ordination issues I would try to do some simple gymnastics type activities. Forward rolls, walking along a bench or some masking tape on the floor, just spinning to music, blind man's bluff.
For the hand eye co-ordination just throwing a nerf ball back and forth or once that's mastered tossing a nerf ball to him to be hit with a small racquet is good fun.
If there are fine motor issues than playing with clay, lego, beading on thread are good activities. And coloring, of course.