Hi, if a whole family apply the US travelling visa, it is the most easiest, but you no need to mention 探親, that means no need to write your US relatives information on the application form, only apply it for travelling purpose. Moreover you need to bring all documents which US dept wants, there is no problem. Enjoy your trip!
簽証容易 (as long as you don't appear like you want to go to US, stay there and not come back to HK, i.e. you need to be able to show strong ties with Hong Kong)