Is purchasing a teleconverter worth it?

I'm going on an expedition to South Africa. I want to be able to do some wildlife work and wondering if bringing a teleconveter is worth it or if I should just crop for reach. I'm planning on bringing my Nikon d810 and 70-200 f2.8. I've done some research but every review ends up being inconclusive. There's some great places to rent higher focal length lenses but i'm not sure if I want that weight. Does anyone have any experience using a teleconverter with a 70-200? Should I get one or just crop in post?

Edit: okay, you guys have helped validate the purchase. I'm now thinking 1.4x or 1.7x. 2x seems to not be worth the loss of light. Thoughts?