An even better way would be to ditch the Keurig and make your coffee in a camp percolator on the range top.
The propane range uses NO electricity. And I would suggest that cobbling together multiple inverters, or running ANY inverters for any purpose is going to cut substantially the useable battery time available.
If you are determined to use these things, then in theory, what you propose might be a good idea. At the same time, I'm not at all sure you wouldn't be better served just adding one or two more batteries to the battery bank. It depends on what devices you want to use.