Re: Training a kid with autism
Kristian I can't offer specific advice myself, but will ask one of my fellow coaches--our box conducts a class specifically for special needs kids and does so working with a local Special Olympics group. Each of the coaches participating had to complete some training done in conjunction with the local Special Olympics group. You can find some of those resources on the internet (I was quickly about to do so with a Google search).
In terms of exercise for kids with autism, I have helped sponsor a friend's son who is autistic and participates in triathlons. I've not personally been involved with coaching him, but can tell you his Mom and Dad rave about how much fitness and training have helped him. The training is his "safe place" and helps him with other aspects of his life as well.