Depending on the number of people in your group, you could potentially just buy 2 four-day passes for each person. That's what we did in 2009. (There are limits on the total number of Salute-priced tickets you can purchase per offer period, but I can't off-hand remember what that number is.)
I don't think you have to be staying at Shades to purchase tickets at their ticket office. You just walk in and show your military ID. I DO think you have to be staying there to purchase them in advance. What I've heard is that in order to make advance FP+ reservations, guests can fax ticket purchase requests to SOG and they'll give guests the ticket information to link to their
MDE before they actually arrive at the hotel. I haven't purchased tickets at SOG in advance before, and I haven't been since FP+ started, so I could be wrong.