Buses from Xian Airport to City Center (Bell Tower)

I and my family will arrive the city on 18 January 2019 and I am not sure what bus number I can take to get to city center (bell tower) from xianyang airport? If I take taxi, how much it would cost? Would one taxi fit 6 of my family?
I heard the airport link train is scheduled to be open in December 2018. I am not sure whether the train will already be in service the day I arrive?