I spent most summers up there as a kid. Her family are farmers, hunters and trappers, and they are quite savvy about what is going on in the area. These folks are out on the land most of the year for one reason or another. They know every person, and every bear for many miles around. I am not kidding you. Every bear.

Yes I agree, I thought of them breaking into empty summer cabins. But it is risky. People come up to their cabins to snowmobile, ice fish and have deer camp. Word would get around pretty quickly if there were a series of cabin break-ins.
And if someone is using the deer blinds, etc.

The other problem is going to be heating the cabins, many of cabins will need wood for heat, and most summer residents won't have put up enough wood for the winter. I guess they can cut some. Also they will need supplies and have to go into the small town store which is very risky.

Of course my cousins could live off the land, but these idiots probably can't do that.

If they had some friends or family up there, could live in the basement, barn, attic, that might work.
But that is risky, I assume there will be a reward for capture, and severe consequences for helping this couple.

Yes I think you are right. They might do better in a more touristy area near a large population center. I highly advise them to stay away from the very rural areas. The farmers, trappers, hunters will have them for lunch if there is a reward.