Is he a kid who is highly self-motivated? Or is he going to need a lot of structure to get anything done?
There are a lot of ways to proceed, some as rigid as school-at-home and some very loosey-goosey. His personality and yours should determine where you fall on that spectrum.
I'd recommend taking a bit of time to get yourself organized and to give him a break. It's called deschooling, and it's a great idea to prevent your both going out of the frying pan and into the fire. Catch your breath. During the deschooling time, let him read, make stuff, think, daydream, watch educational TV and play educational video games, etc. for a while. (Do limit the amount of media time if you tend to go that direction...) You can then take a few weeks to figure things out and not just buy the first thing that comes along.
The first thing I would do after stocking up on books for the deschooling time is to figure out the laws for homeschooling in your state. They're all different, and you want to be sure you're not doing anything that will cause you grief.
The second thing I would do is surf the 'Net a bit and figure out what style of homeschooling appeals to you. Your style will probably evolve as you go along, but it's nice to have a starting point, in part because there is SO MUCH STUFF out there. Choosing to be an unschooler, for example, would drastically change the sorts of materials you'd consider. Not all need formal curriculum. I'm an eclectic secular homeschooler, which means that I can pick pretty much anything I want to use. This year, that means we're using no formal curriculum whatsoever for our DS7, though I could definitely use something if I chose to. I have lots of bits and pieces that I use--workbooks, library books, computer programs, websites, etc.--but we're not starting at point A and moving through to point Z in anything specific.
Does that mean I think this is what you should do, too? I have no idea! Your family's needs may be completely different from our family's needs, so your approach may be radically different. But I would tell you that the BEST advice I ever got about homeschooling was that you shouldn't plunk down a bunch of money on ANY curriculum the first year. You just don't know enough yet to know what to invest in. Dip a toe in, and starting with the cheapest curriculum isn't a bad idea, just so you don't waste a lot of money. Remember that most packaged curricula are made for ND kids, not GT ones. You're probably going to go through things pretty fast. That gets expensive. There are cheaper ways to get the same result...
Here are a couple of useful websites for figuring out how you want to approach homeschooling:
http://www.homeschooldiner.com/guide/intro/approaches.htmlhttp://www.brightkidsathome.com/curriculum.htmlhttp://www.hsc.org/144.htmlhttp://www.midnightbeach.com/hs/Files.faq.htmlhttp://www.hsncincy.com/creating_a_curriculum.htmlhttp://www.hoagiesgifted.org/homeschool_curricula.htmhttp://www.uen.org/curriculumsearch/SearchResults.do;jsessionid=8CE9D01FA0B4144FD3A2351997210343
I strongly recommend poking around on these sites beyond the page I linked to here. They're very useful!
Once you're a bit further along, these are some sites that you might find useful, so I'll post them for you now. But this is really for later.
http://www.secular-homeschooling.com/index.htmlhttp://www.smartteaching.org/blog/2008/08/100-essential-web-tools-for-homeschoolers/Above all, don't feel rushed. I know it's hard not to, but consider the deschooling time a prep time for you and a mental health break for your DS. You need time to figure out what to do, and you don't have to marry the first curriculum you kiss.
Finally, CTY and EPGY courses come highly recommended. I'd look there for sure for a 12yo.
If I can help more, let me know. I know how scary it is to do what you're doing!
But HSing can be a really good solution. At the very least, you've shown your son that you mean business. That's a good thing for him.
