I saw several Teslas around the park, and I think it's doable if you only want to visit say 1 or 2 locations, but without a Supercharger in the middle of the park, you will be limited and won't have the flexibility to see everything.
The resort in the middle of the park has 4 J1772 chargers, which would help if you were staying in the park overnight, but we were simply doing day trips.
The story for the north rim of the Grand Canyon is similar. In the Tesla, from Flagstaff, you must first drive to Page, AZ. Round trip 508 miles and 10 hours. In an internal combustion, its 422 miles and roughly 8.5 hours. When you arrive at the north rim in the Tesla, you can’t go anywhere else, and you must return the way you came.
Tesla should work on optimizing their National Park experience, as it’s the classic destination of an old fashioned American road trip.