If your son is happy and thriving, then you are probably most of the way there now, and undoubtedly doing a great job.
There are lots of homeschoolers on the forum who can talk to specifics, but I'll just throw in a general observation. One thing I've heard parents comment on over and over is that when they start providing their child with advanced, challenging curricula, they just cannot believe the speed and gusto with which their child devours it. A common refrain is, "It never occurred to me to give her something at that level before, but when I did, holy cow!"
So one thing you can do is make sure your son has exposure to such materials and the opportunity to find out what floats his boat. These kids can often respond incredibly differently to complex materials than they do to standard classroom pablum, so it's best not to decide, for instance, that they don't like math if all they've ever seen is a Pearson textbook. Give them a little AoPS for a while and see what happens when they experience a topic taught in all its beauty by people who love it - it's quite a different experience. There's lots of threads here on resources for different topics if you're looking for ideas.
