Disney doesn't care that you're an adult.
When I asked a Disneyland employee about the "first visit" pin, I was afraid I'd get a weird look. Wrong! They immediately told us where to go to get one. When I asked another employee if they still had any left, they gladly gave it to me without any odd looks. It was the same experience when I took photos with Pluto and Minnie Mouse or waved hello to any character. Disneyland doesn't care that you're an adult visiting and won't make you feel weird for being there.