If you do book with a connection, or if they are involuntarily rebooked on a connecting itinerary due to a cancellation, I would check the age rules in the country where they will be connecting. If they miss their connection and have to stay overnight somewhere, can they then get a hotel room themselves or will a parent have to show up in person at the hotel and confirm that they are allowed to stay there? If they risk being stuck overnight without a hotel, then it's better if the connection is somewhere else instead.