heh, i am making one as well for my cousin, he is barely 3 but honestly, he really likes bows (and the tools i use, i had to catch the bugger because he kept taking my plane and grinding it against the cement... not a pleasant sound to hear, and not a fun thing when i need it sharp heh.) in my opinion, if they show an interest, make them one, if not, make them one for later in their lives, either way, be careful when you give a super young one a bow, they will bash it up if you arent careful (well, my cousin will for sure, he's a little demon)
the reason i really wanted to make him one, is because i had a stave break during the splitting process because my wedge hit a knot and decided to break off there, a perfect length for a "longbow" at his size, i figured, rather than throwing it into the fire pit, ill jump on the bandwagon and make him one,
its a shame i don't have any dry hickory left, those bows are almost kid proofed naturally, after all, there is a reason that wood is used in tool handles, can handle an impact
(im going to cut off here, before i get off topic)