I wouldn't really worry or call it real aggression. The snake had an off moment, it's going to happen. Maybe it wasn't your normal handling time, or your snake was just out cruising and you startled it, or it's close to feeding or shedding time, or maybe the teenage angst I've seen Adam make mention of. Could be tons of reasons why it had an attitude on at that moment.

As far as kids and snakes. We have a 5 year old son (as well as three older children). Every one of them has been taught that whether it's a snake, rat, cat or any other pet they have to respect the boundaries of that creature. If they want to handle living things, they need to know it's always about what that particular creature can accept and not about what they want to do right then with it. They can learn a lot about patience, respect and how to sit quietly and observe animals that way too. It also does not hurt a kid to understand that any living thing has the right to defend itself or just have a bad day and needs to be left to itself right now.