How short do your shorts have to be in China?

This summer I am going to on a trip to China. There is just one problem, my family thinks that my shorts are too short and would offend Chinese people or be illegal because they are a bit short. My shorts are mostly hollister shorts (not bermuda) but they cover my butt and some of my upper leg. I don't want to buy new shorts because A) I would not wear them after wards, thus being a waste of money B) I heard it was really hot over in China and if my shorts were longer I'd feel too warm and uncomfortable and C) I'd get awkward tan-lines. I know this all sounds ridiculous but it would really be helpful to know how short most chinese teenage girls wear their shorts or if chinese people would be offended by the shorts I wear. I also don't want to come off as some prostitute or anything else like that either.