If I was in your shoes I would stay with what you have and buy the tele-converter or a lens if you want. I am sure your very comfortable shooting the camera you have now. The D800 is not the easiest camera to shoot and has a learning curve that comes with it. If you have great shooting technique you might be OK, but there is a lot to learn about this camera. It does take some great pictures when you get it right, but you also have some big file sizes too depending on what format you shoot. You could shoot in DX format with the D800 to get your 1.5 crop factor but you might as well use your D7000 if you’re going to do that.
The D7000 takes great pictures also and the gear you have is already to go that you have used before. Yes I would buy a good tripod and cable release if you don’t have one for ether camera. That would be a must for the D800 no matter what! And yes I would get the 300mm lens and tele-converter if you want to shoot bears and other wildlife in Alaska unless you want to get right up next to them. So I say your best choice is No. 3
Not sure what version of the 300mm you’re looking at but the F2.8 always cost a premium and has VR for the money. They are both sharp but the F2.8 weighs more. Unless you need the light or VR I would get the F4, just my two cents worth. You can look at this review: http://forums.dpreview.com/forums/post/41968994 or ask in the lens forum for more information.