Their isn't a "Youth Bow" tag. You can use a bow during the youth season, but will not be allowed to tag a deer with that tag during archery season. This is directly copied from the 2015-2016 Iowa DNR Hunting Regulations Book
Unfilled Youth Tag
Youth hunters with a General deer license who do not take a deer during the youth deer hunting season may use the General deer license and unused tag during the early or late muzzleloader and one of the two shotgun seasons ONLY.
So he can get a Statewide Bow, Statewide Early/Late Muzzy or one of the 2 shotgun seasons, and then get a youth season tag. If the the youth season tag does not get used during youth season, he can use it for the seasons listed above.
We use this for my brother every year and its very nice to be able to use the youth tag in any other gun season to help increase their odds of getting a deer.
Hope this helps! You can pick up a copy of the regulations I know for sure at Gander Mountain and there are probably many other places also.
Happy Hunting!