It's not kids unfriendly, but it is large and very very crowded. There's also a relative lack of facilities, like food is limited, you definitely can't drive there, queues for some of the toilets, so those things might be concerns. Would you take your kid to a large, slightly disorganized music festival? If yes then you should be alright.
I have seen a couple of kids there who themselves were super interested in FOSS. Admittedly, I'm guessing they were at least 12 years old (I'm pretty bad at guessing ages), but definitely one of the highlights of my attending last year.