Go buy a nice 300 Win Mag and you will have a rifle and cartridge you can hunt all game in NA with. This is only your second hunt in a life time of hunting, think forward a few years you may want a grizzly or polar bear, bison or musk ox, maybe you'll go to Africa or Asia. The 300 WM is up to all of this except the really big stuff in Africa.
You can shoot like a lazer with 150 gr bullets and you can hit like a sledgehammer with 220 gn Partitions, for bison or big bears. If ever there was a one size fits all for ungulates it is probably the 300 WM or one of it's close cousins. It is also one of those cartridges that will be in any backwoods hardware or convienience store that sell ammo.
This also tells your future F-i-L that you are your own man and a self thinker and you can use all these points I have just made to justify your position.
You therefore become a forward thinker in his eyes and you are also being frugal because you will never need another rifle for any hunting you may do in the future almost anywhere in the world. (need has nothing to do with want, take from a guy with more than 100 firearms)
JMHO.