Dish pay-as-you-go would not help as he uses the service every month unless he meant every month during the Summer only. Both DirecTV and Dish will allow you to pause the service for up to 6 months if he is using the cabin at least 6 months per year. The services usually have a nice start up price for newbies and will install and provide hardware at no cost with contract.
To the OP, do you know what cellular services work at the cabin? T-Mobile, Verizon, Sprint, AT&T? You can look at a coverage map from each service to get a general idea but nothing works like trying it or asking a neighbor.