Within a single day, yes that's true. So if you have breakfast at the Beach Club, and dinner at the Polynesian, you would only pay the $6 once - they'll give you a dated piece of paper to put in your windshield to show you've already paid. But you should tip each time (when they return the car to you).
Edited to say that I didn't know about the handicapped parking pass thing, but that's probably right.