What shall I do on my 2nd day in Xi'an?

Hi!

First of all, I didn't even want to go to Xi'an in the first place, but I needed a stopover between Datong and Chengdu and thought I might as well do the Terracotta army, although I'm not super interested ...
I now researched what to do on my second day or if I just should leave early, but that would be a shame.

Now, here are the options:

Day 1: Teracotta army (and then either go back to Xi'an city and do as much of the following as possible until it gets dark: Big Wild Goose Pagoda, Bell and Drum Tower**, Ancient City Wall,** Great mosque + Muslim quarter) - those are all optional, but of course would be nice to see

Day 2:
Day trip to Huashan or
Day trip to Longmen grottoes

Or: do not a day trip at all and change Day 1 to:
Teracotta army then Huaqing Palace (+ Li Mt. or maybe hot springs there) and then do Xian city on day 2.

Additoinal Info:
I need to be back at Xianbei Sta. by roughly 6pm as my train will leave around 7 pm.
I already do the grottoes in Datong, so not sure if it's worth doing the Longmen ones as well.
As I'm also going to Zangjiajie, not sure if I really would need to visit Huashan. I would love to decide spontaneously, but as wel all know that's difficult to do in China, train tickets etc. might be sold out on the very day ....
I'm also afraid that Huashan might be a too close call if I have to line up many times ....