I just wanted to jump in since you mentioned buying direct from Disney and wasn't sure if you meant at Shades of Green? If not, I recommend looking at them as an option. Their Salute tickets are about the same price as on base (maybe 3-5 dollars more).
You can order over by email with a follow-up call to pay for them via credit card, but since it's so close to your trip, I'm not sure how they'd handle that since they FedEx tickets. You can also buy in person when you get there.
https://www.shadesofgreen.org/experiences/attractions
We've booked reservations late in the game these last several months, and once or twice the same day/week. The one park I'd be concerned about is Hollywood Studios on the weekend since it's a holiday. (We went during MLK week and there was full availability though. I picked up a second DHS reservation the week before when we decided to change plans.)