I grew up with a neighbour 2 years older than me with Down Syndrome. We always had to be extra careful with him and do our best no to push him into something he doesn't like. But other than some things (some small, some not so small), he's a fully functioning being. I often think to myself, had he had just a bit more luck, everything would be ok.
Man can speak properly, read, write, count, can use any piece of technology you want him, can drive a bike, drove a car with his dad, he goes to a special needs school, he jokes with us all the time and can understand almost all social context you throw in front him. It's just that little something that's missing and that's what makes me sad.
But at least I think that we, kids, back when we were like 6 or 7 years old, we helped his parents a lot by not excluding him. A stupid example would be that he would always play football with us whenever we would play. So my point is, you really need some sort of help with kids with special needs. It's not a one person job.