thanks all for your replies. i should have included more details - i leave in Guangzhou Zhujiang new town, and am traveling with my wife and our one-year-old daughter.

anyway, we just came back from fu tian. took the high-speed train from Guangzhou south station (40 minutes only to Shenzhen) and transferred to Shenzhen metro to fu tian. the queue to enter Hong Kong took us a good 30 minutes, although others all worked out pretty fast.

wasn't very happy with Guangzhou south station as it's far from city, therefore we took Shenzhen metro to lo wu on the return trip. the train from lo wu to Guangzhou east station took 80 minutes. had kfc upon arrival at Guangzhou east station before taking metro home. the whole journey took us 5 hours and 30 minutes. not bad.