First wear some kind of buoyancy aid. I believe it is mandatory almost everywhere in the US for kids.
33 CFR 175.15(c) provides that no person may operate a
recreational vessel underway with any child under 13
years old aboard unless each such child is either wearing
an appropriate PFD approved by the Coast Guard or below
decks or in an enclosed cabin. If the child is observed
above deck without a PFD, then a violation has
occurred.
