I generally don't let *ANYONE* drive my equipment, not even my own family. My Suburban, and bus, both have quirks and personality of their own, and I like to keep a close observation on things so small problems don't become big problems.
The Suburban has a leaky radiator (which I have the replacement), so it loses coolant and will run hot if not watched. It loses like a gallon every 3 months, so fixing it has not been a very high priority.
The bus, well, it's a 30-year-old mechanical diesel, my family is not familiar with driving such a large vehicle.