I am 47 years old. This is my First Anime Convention. I know how you are feeling; I have to deal with the same question. Foremost of all I am a part of the Furry fandom as I walked down the halls this weekend I see much of the same under 24 demographic at Kumoricon as I would se at any furry convention. It is nice for me so see some older fans and families. I kept to my self this weekend for the same reason. I am part of a Portland Furry group and I am the oldest. We do have our own meet ups and yes I feel I am the odd man out. My view to the age issue is to act my age but still be approachable.
I do not know not of meet ups in the Anime fandom but Greymuzzles (furry fans over 30) are not unheard of.
My interest in Anime is a branch off of my interest in Science Fiction so I am attracted to Science Fiction and Space Opera them in Anime but they some exceptions. .
Please not I do suffer from a life long writing disability so please forgive me if my grammar seems to be clumsy.
PS if you do seem me with my con badge "Acton" and perhaps my fox tail do say hello.