Hello Megan & Welcome to the forums.
Sounds like your little guy is one smart cookie!
What types of topics/subjects are you looking to begin teaching? Are you learning towards a particular style? (Montessori, Classical, Waldorf, etc).
Some parents find that keeping boys engaged is a little trickier than girls because they seems to be more active in general. Sounds like you did a great job keeping your son interested in learning, did you use any specific methods or techniques that worked especially well for him or was he just naturally drawn to it without any creative approaches needed? Also, have you tried downloading any of the files for him from the community downloads, like foreign language and so forth? Maybe he would enjoy that for some new material.
So glad you found us-- you definitely came to the right place, it is a wealth of knowledge!