Hi Ed,
I think this is a great time to do some father/son bonding with a hobby you both can enjoy and learn from. Your son will also benefit from the responsibility that comes with keeping a live animal. It's a very forgiving hobby in the sense that if he forgets to feed or clean a cage once, it wont end in disaster or tragedy.
As was already suggested, visiting a reptile show would be an awesome day trip for you. Not only will your son be exposed to the wide world of reptiles, but there are also so many vendors selling dvd's, books and other things to educate yourselves on the hobby. REPTILE magazine is a really good periodical as well. Perhaps there is also a local herp society in your area that meets regularly where you can share your interests and experiences.
As far as a beginning snake, you cant go wrong with a small species of kingsnake or cornsnake. The color variations will make your head spin. Spend some time here on those two forums to find the one for you.
Just be warned, I know a member here on Kingsnake that bought one King to enjoy with his son and now owns around 100 snakes. 
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1.0 Albino American alligator, "Smoke"
1.1 American alligator,"Al Bite Ya & Molly"
1.1 Purple Albino Reticulated Pythons, "Gumbo & Abita"
0.1 Eastern Gaboon Viper, "Gabbie" Recently passed away at 24 years old 