Hey 'bloke:
What's worked for me in the past is similar to what you're doing altitude-wise, but with far less mileage. I choose to "taper down" just before the big dayhike while up at the Portal and instead rest up. Here's what I'd suggest:
Thursday afternoon: Since you're coming from the Bay Area, and likely going through Hwy 120 and down Hwy 395, stop off at Mammoth, ride the gondola to the top, get a bite to eat up there, and spend a few hours up hiking around up top. Of course, this is dependent upon the time of day you drive over and how much time you have.
Friday: Hike from the Portal to Lone Pine Lake (an easy hike that familiarizes you with a portion of the trail that you'll be hiking in the dark); take a book, fish the lake, and just relax for several hours while breathing in that 10,000' air. Rest up.
Saturday: Drive down to the Inter-Agency Center, get your permit, and then continue driving over to Horseshoe Meadow; take a chair and a book, fish the small creeks, and just relax while breathing in that 10,000' air. Rest up.
Best of luck to you -- and take lots of pictures.
BruinDave
