I agree,
if you can't get a campsite at Whiney Portal, you shold really think about Horseshoe Meadows. The elevation is GREAT for acclimatizing, (sp?) and it's generally a LOT easier to reserve. The drive to the portal is only about 20 mins from there.
RE: Parking;
Depends on what time you start .. If early enough, you may find a good parking spot. Otherwise, just drop everyone off and find parking down the road. I've been lucky enough to find parking right next to the trailhead, and also have had to park a mile down the road .. luck of the draw.
Good luck,
...tg...