these are all great choices. the problem is one day is not nearly enough. you can shoot for a week just in downtown. just be careful where you go. some places are not too safe with a camera hanging around you neck.
the Vello grips are one of the more expensive third party grips and I really don't think they are any different than the rest. all seem to be about the same in build and function. I use a Neewer grip on my Nikon D7200 and it does everything fine. 35.00 vs close to 100.00 for the Vello. I have a Neewer grip waiting for my D500 to be delivered. got the camera used for a steal so the free Nikon grip didn't happen. I agree that I would not put it on a tripod with a long lens, but I wouldn't do that with any grip. I have used it on a tripod with short lenses without any problems.
while I agree that vets need better care, I have been treated at the Hines Veteran Hospital and have not had any problems in over 15 years. I know I get a bit extra because I am a wounded vet, but not all vet hospitals are like the ones poorly run and which make all the headlines. I never hear or read about the ones that are run the way they are meant to. I would like to see the US spend less on fixing other countries problems and spend more on the problems at home. we as a nation should be ashamed of the amount of veteran suicides and those living on the streets. of course this would put a dent in the pockets of the elites.
if it's a choice between the two, I would get a Sigma or Tamron 150-600mm. no need for the tc. I do agree that a second body would be best if you can swing both.
I got a Debao from China for a fraction of the Nikon price and like it better. it has more range, can be rotated, and uses AA batteries. I use it with two SB-600's and with my Nikon R1 wireless speedlights. check them out on e-bay.
be careful on those "Nikon" grips on e-bay. box says Nikon as do the grip but I don't think they are really oem. 95.00 as opposed to 250.00 for a new grip. I use a Neewer grip for my D7200. works as it should except it will always use the cameras battery first even tho I set the camera to use the grip battery first. I red this may be because I use a Nikon battery and a third party battery. I ordered another Nikon to see if it's the issue. the oem grip is built like a tank. I had one on a D300 and these third party grips are nowhere near the quality, but if you are not hard on your gear, they are ok for the price.