The freeze dry backpacker stuff, while pricey, is a great meal... assuming you can get hot water quickly. Ever think of keeping a metal water bottle near the engine on the snow mobile? It'd stay warm/near boiling depending on how close you kept it. So, that could be once source of near-instant hot water.

Otherwise, I'd skip the MRE stuff, on the chance it freezes. Def. the mainstay bars or millenium bars, but they're not super high cal, and pretty dry. Being a snowmobile, why not just a can of chili or stew that you can stash away somewhere? Like the water bottle, if you keep it near the engine it could stay warm and be ready to eat whenever you are.