Took my son to his first Comic Con (DC)
dccon_09 by AgeOwns.com, on Flickr
We both dressed as ninjas. This was his first con, and DC's first comic con.
He got a Dirt Boss Transformer, but for the most part, 90% of the tables were comics. I also got him Marvel Masterpieces #1, which was just illustrations and no words (he's just learning to read) and he really liked that.
He said he'd do it again sometime, so we're planning on hitting Baltimore in September.
Here is a write up and Cosplay gallery
That's great, I'm glad he had a good time. As a LONG-time San Diego Comic-con attendee, it's nice to see parents bring their kids to introduce them to the hobby, but only as long as the kids are old enough to appreciate it.
I've seen too many kids that are too young to know what's going on brought to the Con. It's crowded and noisy, and people are pushy and rude. It's not fair to bring a young kid there just because parents are too cheap for a baby sitter.
And those double-wide strollers in the already crowded aisles, how terribly considerate.
Cool How old is your son? I've thought of taking my boys. They are 7, but I worried they were too young. It looks like you had a blast.
I think that is wicked cool! Looks like he really got into it, and I think it can inspire great creativity and imagination. (Can you tell I always encouraged role play/costuming in my kids when they were young? lol!)
My daughter, who is now in college, frequently attends cons (both large and small) in costume and is always happy to interact with younger attendees. Of course, I'm sure that varies widely, and she is planning on going into education so she enjoys young people of all ages, and her costumes are sometimes quite familiar to young children. From what she has described, certainly smaller events tend to be more-kid overall kid-friendly; not as crowded or as noisy, easier to see costumes/be seen, etc.
One of her favorite events, while not a con per se, is Sakura Matsuri at the Brooklyn Botanic Garden, in part because so many families attend this outdoor event. Last year, she and a group of her friends attended costumed as characters from My Little Ponies, and young children recognized them in earnest. They had the best time meeting and interacting with their young fans and managed to get some simply adorable photos. She's going again next weekend & can't wait! 
Of course, she (and her pals) often attends huge events like NYCC, Boston Comic Con, etc., as well as assorted smaller venue events.
He's five. I took it real slow. He was happiest when he found a toy. He wasn't impressed with the rows and rows of boxes of comics.