You may go to Macau from Guangzhou by bus. You can take the bus at Xin Guang Plaza, Rosedale Hotel, Jinhan Exhibition Center, Hotel Landmark Canton or Guangzhou Hai Tao Hotel. Macau is very small. It's renowned for casinos. There are no so many tourist attractions in the city. The main sights include A-Ma Temple, Ruins of St. Paul's, Grand Prix Museum, and Monte Fort and so on.

I suggest you stay there for two or three days. Then, take a ship from Macau to Kowloon. Just take it at the Macau New Maritime Ferry Terminal.