Our kids are no doubt the future, and what we have today will be carried by them tomorrow. So there is no point in keeping them away from bitcoin.
Few things we need to understand in this regard are that with Bitcoin, kids can gain access to age restricted sites like gambling, etc. Since crypto based sites are open for everyone.
We may start telling kids about Bitcoin once they are a bit grown up and use Bitcoin under the supervision of parents.
I can remember me myself in childhood and I'm sure kids can get access to web sites with age limit if they'll want to, not depending on using bitcoin or not. The most correct way to prevent that IMO is to tell them about risks and stay honest while talking about difficult things. And teaching bitcoin is among the things we should do for our children and their safety: trained means safer. They will find a way to know and use it anyhow, we just should try to be the first who will talk with them about all that.