I'm following a Mishnah B'rurah Yomit Seder ...
See SA O"Ch 128:34 re: Duchening by a koton....
Sha'ar Hatziyyun 95 citing Rashi
SA: A minor should not duchen alone MB: even occasionally because it's not "K'vod Tzibbur" to be beholden to a blessing of a minor.
Any "search" on K'vod Tzibbur should include this case.