My personal motto is "It's never too late to have a happy childhood," and that is exactly what I am doing! My husband feels the same way; we are child-free by choice and have been on 57 Disney cruises and countless trips to WDW. When people ask, "Are you here with kids?" we respond, "No, we ARE the kids!" I get soooo excited when I see my favorite characters and shows or when I climb aboard a favorite ride. In my childhood, I had to grow up many years before my time, so now that I have the choice, I let my inner child run free...and Disney is the perfect atmosphere.
And as for the people who make comments and try to make you feel bad, look at it from a cognitive standpoint (the responsible adult part of me is a doctor of psychology). No one can MAKE you feel anything...they can toss a verbal "ball," and you can choose to catch it or to ignore it and let in drop in the dirt at your feet where it belongs. I make it a point to choose the latter...no one but me gets to choose my emotional state!