The general rule of thumb concerning Disney Gift Cards as currency is "if MC/Visa/AmEx/Discover is accepted, the Disney GC will be, too".
"The Richard Petty Experience", though on property, is not a Disney owned/operated function -- therefore, Disney GCs are not accepted, there.
Same goes for anything over at Shades of Green.
Other functions run by outside proprietors include kennels and the golf course (which was recently taken-over by Arnold Palmer Golf Management)
As for fishing -- I am to understand that is considered "private property", if that's the case, it's best to ask your resort or WDW Guest Services if fishing is a Disney-run function...