My son started at 3.  As many have mentioned, keeping it fun goes a long ways.
 
~CB

Start them as soon as they want!  My kids LOVE shooting with daddy, and I gotta say it's one of my greatest joys sharing traditional archery with them.  They are so receptive to learning.  One thing I learned from others when I was starting with my kids...KEEP IT FUN, and they'll keep coming back!

My son Eli's first bow, at two years of age




His second bow at about three.  Since these pics were taken I've cut him down some "custom" POC arrows (daddy loves this stuff).

By next summer I'll be looking to move him up to a newer, nicer bow.  At the really young ages, the plastic and fiberglass is just fine.

His sister Gwen has shown alot of interest and at age six got a St. Joe River bow.  David and Tracy are just amazing and really care about the kids they build bows for.  Gwen's growing into this bow quickly!  These two pics are about six months apart.

Started my boys when they could walk.My first grandson is almost 3 months old and has a Maddog Pup waiting in the bow rack.

Both my boys began at 2...as soon as they could figure which hand to "let go" with.  Make games and have fun is key...don't get caught up with form or anything like that till they are "ready" which for my sons was around 5.  That's when they could take instruction pretty well.  

I envy you guys with youngsters....don't know "when" I'll get grandkids (or even if) but looking back, it was a fun magical time when they were "growing up" in archery.

My grandson is 3. It was 15 deg. the other day and all I heard was "Papa let go shoot our bows".
He is Gene and Barry's bigist fan just loves "Primal Dreams".
I'm sooooo Lucky!

sooner the better Bro  

My 4 year old wears has been tinkering with it for a little over a year and has better form than I do. She usually hits the vitals on my deer target from 5-10 yds. Daddy's proud  

3 yrs old for Emma. Cherished memory below.
 http://www.youtube.com/watch?v=XXNYx7UA0LE

Thank you for the replies, pics and vid. Precious moments indeed.

My daughter started just under two years old , keep it fun for them! She still shoots almost every time I do and she is seven now!!!