CA, welcome to the site. I've posted miles of help on glacier park both on this board and on photo.net. You can search photo.net.

check this site for more info, some may have been lost in a crash many months ago.

Anyhow.

there is no best time, there is no optimum time there only are trade offs. You have to decide what you want to shoot and go for that but be willing to completely change plans.

for a ballpark, plan for the first week august, but never before July 4th. Keep in mind that three are lots of photo tours and other's doing what you propose. You will find 10-50 people at Wild Goose Island every morning the first week of august. The days are VERY long so yours will start at 3-4am if you want to get optimum light.

Keep in mind that the east side is the best in the am, with the west side the best in the pm.

do some more reading as I suggest and then get back to me with more specific questions.

Right now it's 20 degrees, light snow, couple feet on the ground, and th forecast is for 8-10 inches by saterday night! Glacier Park is the center of the universe!