Glad to see you back around the threads, Marion.
The crucial thing with words like boys and girls is that the same ones apply for people whether they've got any kind of a disability or not.
So I'll admit to referring to my son, who hasn't got a disability, as a boy, even though he's only a couple of years younger than my daughter (who was 34 today); and I find it more natural to refer to her, and to the care workers who share her life, as "girls" rather than "women".
But I'm strongly against any way of talking about her as if she was a child, and I've often got into arguments about that wit other parents. Of course the thing is there is an ambiguity about the word because although your son and your daughter will cease to be "a child" omce they are past a certain age, they will always be properly described as "your children" until the day you die, even if they win a Nobel pPrize.
And it's always "people first", and everything else a long way behind.
Thanks for the l'Arche links. Here's a link with lots of interesting stuff, and other links. Since it's Canadian you'll likely have come across them already.