No, I don't think so. I'll probably still have some kind of gaming habits when I get to your age (I'm 27). Lots of my older friends play too.
FO3 is marketed a bit more at a younger audience, but there's no age limit on it. From an RP perspective, the player character is a young man/woman in the games, but I very regularly roleplay older characters in Skyrim, Oblivion, and other games. There's nothing weird about it, just creative and imaginative.