Are you going to be in the boondocks?
Are you going to populated areas (read: places likely to have cell coverage), or in the boondocks? If you're going to populated places, personal wifi hotspots are relatively reasonably priced these days. Definitely get the unlimited plans, and check coverage. Nice thing about personal wifi (or "Mifi's") is that they generally hook up up to 5 devices w/ no other hunk of appliance on your end.