LW#2: Why are you monitoring what someone wears under the privacy of their own bed coves? The rule should be if they get up in the night to go to the kitchen or bathroom, then they need to put on a robe (shorty, lightweight one will do). The robe can lie across the bed in case of emergency. But really. Don't be so intrusive.

LW#1: I think the expression is after three days they stink. But the point remains that you no longer want to host, so don't do it. You don't need to pay for their hotel, that's just unfounded guilt talking. Showing them around will be gift enough. But if you can snag any special discounts, you can pass those along to your family. 

The time to tell your family is before they plan their next trip. Just say they are model guests, but you are set in your habits, and you will enjoy their visit more if you are not hosting. It would be a nice gesture if you can say you would be pleased to host them to a special dinner (at your home or a restaurant).