The cosplay community is a very diverse one. People of all ages and sizes come out to show off their costumes. A friend of mine turning 30 thought that he might be getting too old to cosplay. You're never too old to cosplay. You get gray hair, then you cosplay Gandalf or Obi-Wan Kenobi. Even when you get married and have kids, you don't have to give up your hobby. Bring the kids too!
Often times you'll go to a convention and see Batman pushing a baby Princess Leia in a stroller. Or maybe you'll see Captain Kirk with a mini Mr. Spock. Kids love costumes, so naturally they're going to think cosplay is the coolest thing ever. They get to play dress-up on a day that isn't Halloween, and people take their picture! Fun for all.
There is a good chance that your kid will grow up to be some non-nerd that finds all these costumed pictures from their childhood embarrassing...but cosplay kids are so freaking cute. Most conventions now-a-days have separate costume contests just for kids, because so many children attend these events. From an outsiders perspective, it seems like these families are having a lot of fun. So enjoy all your family nerd bonding while you can, and maybe someday they'll grow up and bring their children to conventions too.
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