I would suggest leaving earlier than 7 AM. I know that Irvine is pretty close to Anaheim, but there will be traffic to contend with, parking to obtain, and the walk or tram from the parking area. You would do best to be in line for the park sometime between 7:30 and 7:40 AM for an 8 AM opening. The family can apply sunscreen and eat snacks while waiting for the gates to open to stave off the boredom of the wait. Then head straight down through Main Street and through the castle to Fantasyland. Start with Peter Pan and/or Dumbo and then work your way through whichever Fantasyland rides most interest your family. The Fantasyland ride lines really build up throughout the day, so this is the most efficient use of your first morning hour.
Keep browsing the Internet and perhaps pick up a copy of the book the Unofficial Guide to
Disneyland to get a sense of what the park has to offer and what kinds of rides and shows your family will enjoy. There are some great stickies on this board too with all kinds of advice. Especially check the stuff by HydroGuy. And keep the questions coming, of course, as you need clarification or expansion on things you learn.
If you are concerned that your daughter's autism could create extra challenges for your day, you may want to learn about the guest assistance card (GAC). I'm thinking that this might help you bypass some of the waiting for some of the rides with longer lines. Never having used this though, I don't honestly know how this works, but I'm sure some people on this board do and might be able to explain or you could call Disney or even just google the term to get more information.