My husband and I decided to finally take our two children (who both have autism) to WDW last October. Everything went FANTASTIC. My husband tried to bail about a week before the trip and came home eating his words and discussing our next trip.
The young man at guest relations was wonderful. He gave us two different Special Needs Passes. One allowed us to use the FastPass Line (or handicapped accessible entrance). Using the FastPass line was really nice because we didn't get those "Why do they get to go first?" looks from people in line. The other pass allowed us to use our son's stroller as a wheelchair. This allowed us to park the stroller in the handicapped areas for shows and parades. The CM's were really great about these passes (for the most part). We had a few that were a little less than pleased, but it's not their job to pass judgement. My kids struggle through so much in their lives. They deserve to get a break every now and then.
The charachters were also great. We just whispered to them about the kids' condition and they were so terrific. Safari Minnie must have spent at least 4 minutes with my son, letting him touch her nose and ears. We had a birthday breakfast for my daughter's 8th birthday at Chef Mickey's. Minnie actually sat with her and helped her blow out her candles!!
The only trouble we had was when we tried Blizzard Beach. We went on election day and it was packed. There are no accomodations for the handicapped so the lines were brutal. The kids would have enjoyed it, but we only stayed a short time (mostly in the wave pool).
The only other real "tip" that I can offer from our experience would be to "slow down" and "find the joy" of every moment. We made very few actual plans (like dinner reservations, etc.) while we were there. If we were able to see a show or catch a parade, great!! If not, we looked forward to what else the day had to offer. We stayed at Fort Wilderness and the daily ferry boat rides were a huge hit with my kids.