One day while in the supermarket, we saw a boy with only one hand. My oldest, Noah, pointed this out (thankfully, in a quiet manner). My response was: "We all have challenges in life. Some are more obvious from the outside than others. He has one hand. You and I have autism. It doesn't make us any less than other people, it just means that there are areas where we struggle where others might not."
Since then, I've noticed that many of my son's friends are the types of people who might be rejected by "the popular kids" for various reasons (cerebral palsy, autism, or just a general geeky attitude). He notes that these people have this the way you might note that someone has brown eyes - a basic fact about them but not something you are going to judge them on. I'm very proud of both of my boys for being able to see past a person's physical appearance and judge people based on WHO they are and not based on skin color/disability/religion/special needs/etc.
Jason, congrats for being an excellent Dad. I bet that your boys will be examples to their "normal" classmates and will pass on what they were taught by you. With today's day and age of bullying those with various disabilities you're set a good example.