I wouldn't worry about the safety of your family (any more than usual, of course!). China is, by and large, a very safe country, especially in terms of random, violent crime. Of course, you'll have to take care of your valuables, and keep track of your family, but a normal-level of concern for your family is all that is necessary.
Do what you can to eat trustworthy food (ie avoid street food, especially with young kids), and avoid tap water entirely. Bottled water is cheap and everywhere- it'll help prevent belly-troubles.
Have a good trip!
-CT.Net staff