Michael Schoch, Answers questions on Noodle
A description from the Iverson Foundation states that all children at the John F Miller School are non-verbal and 95% are unable to walk. The school seems to have a fairly large and well-trained support staff. Since the school doesn't have its own website, I recommend calling it at (702) 799-7401 to get more specific information. It sounds like it may be a good fit for your 5 year-old at least.
A list of community networks and support groups for families with autistic members in Las Vegas is available through Autism Speaks. Another local resource is Families for Effective Autism Treatment--a network of support services and specialists.
Noodle also has a list of articles, guides, and advice from experts and concerned parents of autistic children. I recommend reading over some of the advice on that page, as it can help you figure out your next steps.
There are a few other special needs schools in Las Vegas and you may want to call each of them to receive accurate information regarding their faculty and resources.
Best of luck in your search. Autism Spectrum Disorders present difficult and confusing challenges for many families. Don't ever hesitate to come back to Noodle with a follow up question.