Ask each person, before anyone looks at a map, how long they enjoy being on their feet and whether stairs, heat, or cold end the day early. Write that down. A Beijing day designed for a photographer is often two or three outdoor sites plus a night neighborhood. For many parents in their sixties or seventies, that is two days forced into one.
A kinder shape is one anchor in the morning, lunch without a rush, and either a short second stop or nothing. The afternoon is part of the plan, not a failure to fill. Jet lag makes the first two days shorter still. Landing and going straight to a palace is how a trip starts with an injury or a quarrel.
Two or three cities in two weeks is usually enough. Adding a fourth city to “see more of China” spends the extra day on stations and packing. If someone has a bad hip, a heart condition, or simply hates early starts, say so at the beginning. A good route can be rewritten. A ticket already bought for a 7:30 train is harder.