Slight addition to 3): Must have valid disabled placard displayed OR plates on the car.
We drive to WDW so actually have both a placard and disabled plates.
It's much simpler when entering a theme part lot where CMs are directing cars into a row to wave the placard so they immediately see you have one and can point you toward the handicap section.
Plus, should anything happen to your own car, you've the placard for use with a rental.
Don't have to remember to hang the placard when in your own car if your state permits you to get both.
Not to be too hard on self, bsmcneil.

I read your thread asking for tips as a single parent with 2 kids and your followup. Sounds like you did pretty well given the challenges you all had. So, pat self on back and give self a bit more credit, ok?