Before you decide to lower poundage on a perfectly good bow, check out the pawn shops and used bow ideas. Many times if you mention it's for a kid, you can deal with folks pretty easy. Also, since you are thinking along the "modify" lines, many bows that would otherwise be junk, with split tips, etc. become perfect candidates for "projects". I've done this a number of times, and picked up the bows for almost nothing. Got some great kids bows, and even learned a lot about bowyering.