Surely the eight & ten year olds can sign their name. For the youngest one I found
on the government web site http://travel.state.gov/passport/fri...1741.html#ca63
the following inf.
"My child is too young to sign his/her own passport. How do I sign my child's passport?
In the space provided for the signature, the mother or father must print the child's name and sign their own name. Then, in parenthesis by the parent's name, write the word (mother) or (father) so we know who signed for the child."