Are we able to obtain the 144 hours free transit in Pudong Shanghai

Dear Sir/Madam
My son and I are British passport holders and going to fly from London to Vietnam but we will stop over in shanghai Pudong airport on the 13th of Apr 2018 for 3 nights to explore the Shanghai City, we will leave Shanghai for Vietnam on the 16th of Apr 2018.
Are we allowed to obtain the 144-hour visa exemption in this occasion.

I am looking forward to hearing from you.
Thank you for your time
Yours faithfully
Lien Pham Morgan