lutach, I understand a bit about how you've felt with the Autism thing.
My son was born missing some important pieces of his brain. He's basically a 2 year old newborn. He can smile and laugh (which forunately he does a lot) and hold his head up, but he can't speak, can't roll over, can't sit without support and he's 99% blind (he reacts to light). He has severe seizures and requires constant medication and has enjoyed countless nights in the hospital. Fortunatley, he eats like a champ, and he's otherwise as healthy as a kid can be.
There's no name for what he has and there's nothing to indicate what progress he might make or how long he'll be with us. Like your daughter, we're just happy to have him as long as we can have him and the joy he brings into our family. He's not without his stresses, but we'd never give him up for anything. As long as he's healthy, we're happy.
Anyway, this hobby is a great release for the stresses of life. I like to think that my son enjoys it as well even if he can't express it. I often tell him all about how the cars work and tell him my plans for them and what-not. He is a lot of fun and a great kid to be around. Chicks love him too.