I realize this isn't a direct answer to your question, just some related data points. For the last year or two, the original long-term lot that's out beyond Terminal A is always full, all the time. So I end up parking in the new long-term "economy" lot that's past Terminal B and the short-term lot in the other direction. I counted at least 5 Model S vehicles in that long-term lot as I was walking. There are a small number of L2 chargers near the street in the short-term lot (all were in use, so I certainly wouldn't count on them.)
What I would do is charge up to 80% or so, put your car in Energy Saving mode, and then just not worry about it for the 10 days. When you come back, go charge up at Mountain View or Fremont.