If you are going when it's not busy, the handicapped viewing areas are a good spot, but when we've gone during busy times, they haven't worked out well for us. Because they get full, you may have to go there early to get a spot. You might be able to talk to the CM and explain your needs like Lisa suggested.
If you are going at a non-busy time, you might not have a lot of trouble finding a pretty good spot outside the handicapped area without a long wait. Certain areas (the train station end of Main Street and the hub area in front of the castle) will be busy, but finding a good spot someplace else might not be so bad.
One of the places we like is the porch of the building where Tony's Town Square Restaurant is. The whole porch used to be open, but they've turned most of it into an outdoor eating porch for Tony's. The end nearest the train station is still open though and there are several rocking chairs on that end of the porch. When we travel with Grandma and Grandpa, they sit in the chairs at the rail of the porch, starting about an hour before the parade. Most people looking for spots are looking to be right by the curb, but the porch works well for special needs since you can see well, but are not so close. Also no one can be right in front of you because of the rail and no one can get too close behind because of the rocking chairs.