38 GB is what is needed for the photos alone. This is based on the largest JPEG and NEF files I have from the Nikon D5100. Add video and you are over, so much so that I think you would be tight with 64GB and should go with the a 128 GB version. I have both a 400X and 133X version of the Lexar 128GB SDXC professional and they worked flawlessly until now. Sandisk also makes a 128GB Extreme but I do not have it. I do have some Sandisk 16GB cards in Extreme and Extreme Pro version which also worked without trouble so far.

Now I have never filled either one but there are reasons to have two. Personally, I do not by the you might lose because when you have only one card, it is hard to lose since it always stays in the camera except for downloading and goes right back. What I do buy is that some cards fail and I know they do. You may be one day the unlucky one in a million which has a flawed top-of-the-line card. If you buy a cheap card of course, your odds are much worse. The bigger your card, the more you stand to lose in one go. Also, if one break while you travel you will be sad about what you lost but you can still go on.