Gosh, I get many character autographs per trip, and I never think twice about it! And I am not exactly a kid ...
If I ever feel a tad awkward, I may mention to the characters that the autographs are for my nephew. The only problem that sometimes occur is that often the people behind me in the character's line assume that I am just "standing there" or that I am with the family in front of me, so they just cut right around me. This has happened to me many times over the years - people assume you aren't really in line if you don't have a kid.
But most of the time, getting autographs is fun!
