ALWAYS carry multiple SD cards and batteries.
I've had an SD card fail on me, and lost most of a family vacations worth of digital memories. What I do now is use a new SD card each day, so at the most I'll only lose one day worth, not the entire vacation. Since this is a "bucket list" occasion, I can't stress that enough.
Also, my Nikon has the ability to capture an image, but store it as two different file types. One is "FINE" (or "ULTRA", I can't recall), but a secondary image stored in RAW format. That might make things easier for the person you're sending the photos to. I've been told that images stored in RAW are easier to post process. Obviously, that takes up even more space, but like has been said, SD cards are cheap.
Even though I didn't address your question, I hope that helps.
Bob