Congratulations on your permit!
> 1. Planning to stay at Trail Camp. Do regular tent stakes work and is there sand/ground to stake into? Or do you tie off on rocks or something?
Most of the sites at Trail Camp are pretty rocky or on smooth granite. So driving stakes likely won't work. But there are plenty of rocks around.
Here's a picture from Trail Camp.
> 2. Down jacket or fleece jacket?
I would take the fleece and layers. Consider leaving the vest behind.
> 3. At 12,000 feet in early September, are we okay with a cannister stove?
It should work fine.
> 4. Is there enough parking?
If overnight parking is full, people park along the road.
...ok those are my opinions. Hope others will reply.
And you might find this helpful: Bob R's ultralight pack list