There are wheelchair spots reserved that I saw on Main St. Unfortunately it is not impossible for someone to block those as well. Have you tried having a family member stand in front of your daughter to reserve the spot, then switch and stand behind her right before the parade reaches you? With the new fireworks show there is so much to see besides just the fireworks that no one can see it all. If you can't get into a designated area for the fireworks at least when there are lower fireworks you can find a spot where she can see projections in Main St or Matterhorn.
Thanks. We haven't tried the designated spots for wheelchairs for the Fireworks. Generally I find reserved wheelchair seating/spots at DL to be less than stellar, e.g. Fantasmic's spots prior to the FP change were way off to the side. My usual strategy near the hub is to have her park right behind a fenced off landscaped area that is on a slope. Then I have her brother stand a little ways in front of her to "protect" her line of vision. Lately we've moved our spot to near IASW, and she parks on the raised terrace area.