As far as making the laptop case I would use like a 2-3 oz veg tan leather. You can tool and dye and whatever else you want to do on it. To make is waterproof, first of all, make sure you dont have any large gaps. Then take all your parts (before sewing them, after tooling and dying) and put one even yer of Kiwi Camp Dry Mink oil, The spray on one even layer of Kiwi Camp dry Performance Fabric Protector. Link to Kiwi
The cool part about the Kiwi camp dry Performance Fabric Protector is that if you are out in the woods, going through bushes and trees and the Kiwi gets scratched off, you can just spray more on. Its is also a clear product so yo can put it on all of your leather products that you want to be waterproofed and it wont change the color.