You could go with the 16, except for storing the movie and the TV series for viewing over seas. Video takes up huge amounts of space. High def video takes up even more space. In my opinion, the extra memory is only worth it if watching video that is stored on your iPad is a high priority for you. (Or for someone that wants to have a huge music collection available on their iPad, which is not your situation.)
In the US, low cost or free high speed Wi-Fi is almost everywhere. I can watch movies and TV shows with Hulu, and not have to use up my memory storing them. I can also listen to music stored in "the Cloud" or just listen to Pandora. My photos are available in an online photo album as well.
I have 1,400 photos, 120 apps and dozens of eBooks on my iPad. Out of my 16 GB, 14 GB are used, and 2 GB are still available. If I start to run out of space, I'll just delete some photos and some apps.
When 32 GB memory chips cost just a few dollars, I can't see paying $200 or $300 more for extra memory. You could also try loading movies onto your iPad from an SD memory card using the Camera Adapter. It is designed to load photos and video from a digital camera, but there might be a work around to allow you to load movies and TV shows, especially if they are not copy protected. Some, but not all, USB memory sticks also work with the Camera Adapter. The files need to be in a directory called DCIM. It's is definitely something that should be thoroughly tested before you leave on your trip! But if you, or a techie friend can figure this out, you would have an extra $100, or $200 to spend on your trip.
By the way, the Camera Adapter also lets you plug in an ordinary USB computer keyboard, if you need to do a lot of typing.