Originally posted by aslyfox never been to GC so no idea what I will see or what the light will be
The good light is at sunrise and sunset, mid-day (in summer after 9 or so and before 4 or so) is pretty blah, flat.
for clear skies, You do have some altitude working for you, south rim is about 7k-ft, and north rim over 8K-ft but haze and smoke can be a problem if there are wild fires nearby.
I've been there a couple times, but 30-years or so ago now,
They did have a steam train that ran up to the south rim from Williams, not sure how it has fared from the pandemic shutdowns. If it's running, could be some neat photo ops even if you don't ride it.
In my trips there, I have preferred the north rim, it's quieter (cooler) and more personal, but more commitment, a long single lane highway in and out, the old park lodge there is neat.
My last trip like this with family, to Mt. St. Helens, I took nearly all my gear with me, but only used a single body and two zooms, 18-135 and 55-300, rest of the family does not have the patience to wait for me to mess around a lot. The rest of the gear stayed in the car in the case all of the trip.
it's a pretty part of then world, Have fun,