we have 2 days to spend in Guangzhou and Shenzhen area, what do you suggest?

In Guangzhou, it is suggested to have fun at Chimelong Resort. And in Shenzhen, you can take them to visit Window of the World, Splendid China and China Folk Cultural Village.

Where you are staying in HK? Well, at Hung Hom, HK, take MTR East Rail Line to Lo Wu. Then cross immigration border to Luo Hu, Shenzhen. The whole journey considering the immigration time takes around 70min.