Is it ok/appropriate to wear crop pants and sandles to most of the tourist destinations in China?

Well, I think it depends on what kind of tourist destinations you plan to visit. Take Great Wall for example, I don't think it's good to wear a pair of sandles because you need to climb. In my opinions, it's ok to wear crop pants and sandles to visit city attractions. For mountains and other natural scenic areas, you'd better at least change a pair of shoes.

Unless you are visiting shrines and temples, capris and sandals are fine. Bare in mind though that the ground, even when paved, can be quite uneven, so I would avoid the platform sandals.
If you are visitng the shrines, typically you must cover your knees and shoulders, but generally Sandals shouldn't be a problem