You're taking your better half and her new 30-06 so why not borrow it for croc? I presume she will hunt buffalo too? She won't be doing it with her 30-06. Will she be using your 375?
If you're stuck on one gun, I would suggest considering QD rings and an extra scope. Then you have the option of switching loads for different animals. For starters, a higher magnification scope would definitely be an advantage for popping a croc in the brain bucket. Lower magnification is better for close in shooting, especially if target is an inbound and angry 1700 lb buffalo. Lighter 375 bullets may give you a better grouping. Also might be less likely to blow the skull to bits. Pull the velocity back some on the croc loads and see how that works on paper. Especially with <300 gr bullets, less velocity would be likely to get less fragmentation/deforming after impact. Most of the time a good mushroom is what's desired. But shooting a croc in the skull with a lunker 375 caliber should be sufficient with just the diameter of the bullet alone. I would not want to trust a long distance taxidermist to put a shattered skull back together properly (I'm presuming you want a skull mount and skin, not full body mount - also presuming you don't live in Windsor Castle

). Of course, this is assuming you will have the option of reloading. Pretty much impossible to buy anything but 300 gr ammo over the counter for 375. But much lighter modern tech bullets in that caliber will work, even on buffalo. Ask me how I know! Just make sure if going with lighter copper bullets to put enough gas in the case. With two scopes each being zeroed for their specific load, you can switch loads for different game.