The Milky Way over Ndutu, Tanzania

Great captures. We will be heading to Botswana and Tanzania in May  and I need some help with lens choice. I will  have a Nikon D80, 70 200 2.8,1.7 tele and a  D600. Can I get suggestions for something to put on the D600 for under $2000 ? Sigma 50 500, Nikon 300 F4 ,Nikon 80 400 VR?
Also taking a wide, not sure what the budget is on that.

Thanks