If you haven't read the GAC (Guest Assistance Card) information that is in the disABILITIES FAQs thread, I'd suggest reading that because it might answer some of your questions.
If you've read it and still have questions, you can ask more here.
If you are able to get to the parks early, you will usually find shorter lines, shorter waits and less people. That's a good strategy for MK. I am not able to get my DD ready early enough in the morning, but my DH and other members of our party have and were able to go on all the Fantasyland attractions (some more than once) with very short waits (some it was pretty much as fast as they could walk on). He has done this on several Spring break/Easter trips.
The parks get busy by 10am and often slow down around 2pm, as people who had been at the parks early go back to their resorts to swim, etc. For AK, we've found it is much slower late in the day - last year during Spring break, people in our party went on Kali River Rapids over and over with less than 15 minute waits because it was slow.
For Epcot, the newest ride, Soarin' is busy pretty much thru the day, but most of the other attractions will have shorter waits as the day goes on and the earlier arriving people leave.
It would be helpful to know when different parts of the park are normally busiest - things like the Unofficial Guide to WDW and Tourguide Mike can help with that sort of information.
disneygal66 said:
Having 2 children with special needs, the GAC is a godsend! We used it when the waits were long and we didn't have fast passes but it was there when we needed it. Basically, just go to the FP line and show them the card. They usually let you in and you just walk through the FP line . No one ever has given us a problem with using it. Again, we used it just as needed. Some people will really abuse it. Hope your trip is great!!!!
I just wanted to point out that not all GACs allow the same thing as disneygal66 children's GAC does. Since the individual message on the GAC is based on needs, not all allow use of the Fastpass line.
Whatever the GAC says, show it to the CM at the entrance (the one at the Fastpass line may be the only CM you see) and they will direct you to the appropriate place.
Using Fastpass is still very helpful; when you use a GAC, you are never sure exactly how it will be dealt with. The CMs may take you into the attraction right away or have you wait in an alternate place. If you have Fastpasses, you will for sure enter the fastpass line and that line is usually going to be a 10-15 minute wait or less.
You can send one person from your party with all your park passes ahead to the Fastpass machine to get them. You don't need to all go to the machine.