Sarah you might want to start by showing him pictures on BPNet or elsewhere on the web of snakes feeding. See how he reacts to that as a first step to seeing a live feed.

We have a 5 year old that has never seen the snakes feed. One of the reasons is because I breed our own rats here and he helps me feed and water them. For him the rats are more like pets so we don't want to let him see a feeding quite yet.

I would also suggest talking about the mechanics of feeding, how the snake constricts and how the rat actually dies (stressing it is a natural process for both creatures to fulfill their roles as predator and prey). Kids tend to fear what they do not understand so giving them information appropriate to their age always seems to work best. Stress that the snake is not being "mean", nor is the rat "suffering" unduly. Nature does not make her creatures like that (well except us humans unfortunately). He may wonder if the snake would do that to him (bite and constrict) so be prepared for those kinds of questions.

You're his mom, you'll know when the time is right for him to observe a live feed.