Do characters sign with "for [name]"?

Hi,

I was wondering if any of the characters sign with "for [name child]" if asked. Or if they ever sign anything else besides their autograph.

For example I want to make Anna and Elsa sign a Frozen book and I would love for them to write something like "for [my childs name] [autograph Anna and Elsa]". Or something like "enjoy our adventures [autograph Anna and Elsa]". Do they do things like that or are they forbidden to write anything else besides their names?