For those smaller items you don’t take, but still would like them secure, I’ve heard that the dish washer is a good place to keep them. It’s waterproof and secure.
Other than pictures and other minor things it’s more like a motel room since everybody in the family uses it.
Rule of using it is leave it like you found it. Dishes washed, laundry done, fresh sheets on the beds, carpet vacuumed, floor moped and baths wiped down with Clorox wipes. Mow the grass sometime during the weekend.
Violate the rules and your visiting privileges are revoked.