For F! yes, it is near the Golden Horseshoe. But it fills up pretty quick.
For the buffet they'll just let you park the ECV in the area, at the entrance. If you get the middle section you will need to walk, they'll guide you though. Go to the area where you registered and take it from there. We were told to go somewhere else last year and of course that didn't work with the scooter.
For fireworks I am as confused as you are.
I did spend about 2 hours on the phone and wrote 15 e-mails to various places and was being told last year that no, there was no special area for wheelchair users or ECV users for fireworks. I have it in writing from four sources. That info is from November 09.
IASW and an area near the Plaza Inn are listed as alternate parade viewing, but it's the first time ever I hear about fireworks viewing.