I just wanted to wish you good luck; but also to say that the worst case scenario may not be as bad as you're fearing.
I've known a lot of children and adults with Downs, and, on the whole they've been lovely, happy people. They have challenges to face, and many for their parents too, but they and their families are not doomed to a painful, horrible existence.
My friend was given a 1 in 3 chance. I was pregnant at the same time, and genuinely wished that, if one of our babies was affected, it would be mine (I chose not to have any tests). I knew we'd cope; she would too, but in a different way, and it would be a lot harder for her. Our daughters are both fine, and very good friends.
If you are in the 20%, a termination may well be the best option for you - just don't think of it being the only option. Hopefully you won't have any decisions to make, but if you do, make sure they are your decisions and not just based on what is expected of you.
I'm really glad I didn't suffer from chocolate tasting different; it was bad enough having to give up the alcohol!