Oh，since you have three children and 2 big luggages, I think the best way for you is to take taxi from your hotel to Lo Wu. Pass through Luohu Custom and then take a cab to Shenzhen Metropark hotel. or you may need to make tramsfer by mtr or bus.

thank's for your reply. how much is the taxi fare from citygate to lowu ? thank you

I think Ms Snowycatkin have made a mistake. She may give you the wrong information. Taxi or bus can not reach Lo Wu border in Hong Kong, they can just get to Sheung Shui and you still need to take the East Rail train for one stop to Lo Wu. The taxi fare to Sheung Shui may be more than HKD300.