Please suggest an itinerary for a group of 6 of us to follow in Guangzhou.

Hi, I suggest you spend three days in GZ and two days in Shenzhen, which is around 80 minutes' high-speed rail journey away.

Well, hereunder is my general suggestion:
D1: Sun Yat-sen Memorial Hall, Yuexiu Park and Temple of the Six Banyan Trees are suggested. In the afternoon, you can go to Baiyun Mount.
D2: Chimelong Resort cannot be missed and it deserves a whole day visit. If there is time left, you can also go to GZ Zoo. At night, you can take the cruise to view the Pearl River.
D3: Go to Shenzhen, where you can have Splendid China, Folk Cultural Village and Window of the World (WOW) on the list.
D4: It is suggested to go and visit OCT (Oveseas Chinese East) or Xiaomeisha Resort. In the afternoon, go back to GZ.
D5: This can be a shopping day. Qingping Market can be visited in the morning. Then you can go to Shangxia Jiulu Pedestrian n Beijing Road.
Hope help!