If this is a trip of a lifetime, and it sounds like it is, I would drop anything unnecessary and use what was at the location instead (toiletries, etc) in order to bring an SLR. I have never been happy with phone photos. My wife travels for business to europe a great deal and while her photo pix are fun to see where she is, I would not consider printing them or even using them for desktop photos on my mac. Their quality is just not very good. The cameras do not compensate for changes in light, and have very poor ISO and are frequently quite noisy.
I would bring one body and two lenses (or perhaps one if this was a wildlife/safari shoot) Wide angle being optional. That 100-400mm sounds like a great choice. You might consider renting the lens you would like to bring. Be aware that there are forms you have to fill out when bringing camera equipment into some countries. Make sure you have your serial numbers of your equipment handy.
Dunno, once in a lifetime trips like what your sounds like, I would not want to spend any time regretting you missed a shot of a lifetime. On the other hand, if you just want to take some snaps and experience most of your trip 'in the moment' and not behind the camera, I'm sure you will be perfectly happy with your cell phone and some add on lenses.
Your vacation, so it is your trade off.