I recently made a horse bow for my nine-year old grandson out of osage orange. I use Al Herrin's design which he describes in his book, "Making Cherokee Bows and Arrows."
The bow is 45" nock to nock. I cut the handle about 1.25" wide and about an 1.5" thick. I normally make the non-bending portion 8 inches long. This time I only made it six inches and it seems to work just fine. The limbs are about 1 and 3/4" wide at the fade about .25" wide at the nocks. The bow measured 30# @ 20" and I have drawn it to 26". (I wanted to make sure it could handle his increased draw length as he grows.)
For the arrows, I bought 48" long 5/16" hard-wood dowels from the local do-it center and cut them to 24 inches. I used 120 grain points and 3" feathers. He loves the set up. Its a little heavy for him, but it should last him a while as he grows into it.
Here is a picture at full-draw. I re-tillered it since this picture but didn't get another pic.