If what you want is National Geographic– As wildlife photographs, then get ready for a huge sticker case, thousands of dollars just for a lens and the total absence of anything convenient to travel. (Watch the video of Roger Cicala's lenses on Canon's large white super lens lenses).
I could get the Canon EF 75-300 III, but this is a very limited lens, and you will end up acquiring a technique to use it well or you will end up with many blurry pictures. The 70-300 IS or 55-250 IS models would be better, but they will be more expensive. But you can also consider renting a 100-400L superzoom for the trip. But that is a lens of more than $ 2000 with which you should look and track.
In addition, I use the Canon EF 400mm / 5.6L lens (equivalent to 600mm in my APS-C dSLR) to photograph birds and deer in the back canyons of Southern California and often it is not enough. Just so you have a sense. With wildlife, your field craft really counts for more in terms of how close you can be.
Only me, but I would say that you consider getting a superzoom bridge camera, like a model from the Panasonic FZ series. This is a fixed lens camera with a supertelephot equivalence in the superzoom lens that it has because it uses a much smaller sensor (1 "format or 1 / 2.3" format) compared to a digital SLR camera or without a mirror. The image quality may not be as high, but it should still be higher than what you can get with a smartphone and accessory lenses.
However, you will want to check the speed reviews with which the cameras shoot and autofocus. Wildlife tends to move fast. The shutter delay can be very frustrating.