Absolutely nothing wrong with adults getting autographs. It's a fun thing to do. One person will riding Space Mountain 5 time in a row fun - I like running around Town Square getting into character lines.

First trip to WDW I did my first "ride" 5 PM first day and only because one of the storms started coming in. Before that it was character lines from opening on, only interrupted by the parade.
The characters certainly won't mind. Sometimes I get the feeling that they even enjoy a little break in the "routine" when they get an all adult group.
I draw, so I mainly bring drawings to get signed. That has prompted lots of fun and special interactions. But generally, as long as you are willing to play you'll have a good time.
Gaston joined me on a photo with Belle one year after a particularly memorable meet earlier that day.
At one Halloween Party I was really badly trying to catch up with Pocahontas and kept missing her. The Cast Members noticed and asked her to come over to me after her set really quick. She personalized my picture and could not have been any sweeter. That one almost had me in tears.
Another year I was walking behind the Queen of Hearts by chance and she got really mad about some trash on the walkway. Nobody else bothered, so I decided to be nice and curtsied and picked it up. Fun little moment I thought. Then a little later I found her having a tea party with Alice and the Mad Hatter. When they invited other visitors to join the party people kept pushing in, but the Queen blocked one seat and waved me over. So I got to play tea party.
In Paris I met Cheshire Cat at a character meal. I told him about one of my friends in Los Angeles and how much she loved him and that I wish I could take him to go and see her. I had this silly little idea and asked if we could take a photo where we pretend we walked off together, so I could send it to her and proved that at least I tried to bring him to her. Cat nods, takes my hand... and starts running, dragging me with him! We actually made it past reception, running hand in hand.
Vala thanks for sharing this!!!
Before the Grand Californian character meal refurb a friend of mine and I did the Easter brunch there. We had drawings and a handmade autograph book and caps and hats from Tokyo, all kind of fun stuff. The characters kept coming back to us. At one point we had Kenai and both 'munks with us, and that was although the CMs kept telling them politely that they had "lots of friends left to see." In the end we even got a group shot with all.
Character magic doesn't expire past a certain age.