I would think for a four year old, you would want something like a toy bow with suction cup arrows. I teach archery to kids, and have 8 grandkids of my own, and my experience is that by 7-8 years old, they are ready for a "real" bow of about 15#. At 5, one of my granddaughters seemed to shoot the 15# bow pretty well and I got all excited about it, but the next time she came to visit she was on to something else, as they have a tendency to do at that age. Every kid is different, of course.