Well, here's the post that I didn't get to post the other day when the board went down. Except some of the posts I was replying to went missing, but here's mine anyway:
Thanks TarnLover, I knew this was the place to come. Just having someone point out that an adopted child is no longer a step child is something that when you're in the moment you don't think about. I'm going to contact the adoption people that sent me info back at the beginning of the year tomorrow and see what they say.
Liz - Thanks

Jewlz - Thank you. I'm really lucky that they want a mother figure. Their mum died in 2001 when they were 3 and 5, so it could've gone either way I think, as far as them accepting me so quickly. Sorry you aren't able to adopt your stepson.
And new info:
I emailed the US Embassy in London who sent me to
http://adoption.state.gov/ and that has mainly to do with adopting unrelated children in a different country. I emailed them, and they got back to me today. I still have to go the immigrant visa route, and can do that anytime. They will be eligible for US Citizenship after two years residency with me. That can be here, there, or split any way it doesn't matter. I am thinking of some other details to follow up with them about, but I'm trying to process everything first, so I ask succinct questions that are easy to follow in this complicated situation.