Possibility of a 144 hours staying twice during twenty days

We are a family of four (Ukrainian citizens) are going to travel by the route Kiev-Shanghai - 144 hours staying - Shanghai Hong Kong - one week staying - Hong Kong-Shanghai -144 hours staying - Shanghai- Kiev. So, we would like to take an opportunity of 144 hours staying twice during twenty days with the gap between staying of a week. Is it legal visa-free? Have we got a possibility to do this without getting the Chinese entry permit? Thank you for your answer.