I have an ADHD 8yo that I homeschool and a high needs 3yo. Best thing I ever did was spend the money on a swing set and a sprinkler. We all go in the back yard and play. I even get on the swings with the 3yo while the 8yo is "manning the ship" and then I get to read for a total of 5-7 minutes during runs through the sprinkler. If it's not too hot, I take them on a walk.
Otherwise, the 8yo gets into reading or his Legos and I'm left to entertain the 3yo--which I try desperately to pawn off on Play-doh, scissors/paper, wipe-erase cards for learning to write letters and numbers (I could care less if she does it right, but she wants "schoolwork" and this "qualifies" in her mind ), coloring, paper doll stickers from Melissa and Doug, and letting her think she's scrubbing veggies in the sink when she's really just making a wet mess.
But outside is pretty big. Especially for the ADHD.