For each of my four kids I made a red oak board bow as their starter bow. Super easy. Went to Home Depot, picked up a board (the ones I use are individually wrapped in plastic, 48" long, about 2" wide and maybe 1/4" thick), and a piece of oak 2x2. Used titebond III to glue a handle section and tip overlays, then cut out pyramid shaped limbs, no tillering needed. Let them paint it before I sprayed with poly and done.
Cheap, easy and perfect for them. Started them all before they were three.
I let them carry it around the house strung (no arrows of course) and they would "hunt" their imaginary animals or the heads on the walls! "Arm straight and pull to the cheek" is the mantra we say and they repeat.
Best part is that if they break one, no big deal, we just make another.