Use of 144-hour visa

We are travelling to China from LAX in March 2017. We have a round trip ticket to Shanghai and a round trip ticket to Hong Kong. Both tickets are different airlines, one Delta and one Cathay Pacific. We would like to stay in Shanghai for 3 days, then travel to Hong Kong. On the return, we will not need to leave the airport in Shanghai. Is there any issue with this itinerary? Anything special we need to consider? Thanks.