I grew up on the mountain.
Not saying it's not worth a shot and I don't care about the fees, but I can tell you this.
If you/we are not up there by Friday around 3pm Spencer will be full as will be Rose Canyon (Spencer is #1 choice since it did not burn bad in the last big fire, Rose did and it's like camping at Walmart now).
There are almost a million people in this valley and anything above 6K' is over run on the weekends, especially in the summer.
I doubt we could even get into General Hitchcock, it's lower but smaller.
Gardner is about like Silver, a little lower actually but about the same 10 degree temp difference, more at night.