which one is a better translation and seems natural in Chinese? For the translation of the sentence:  

Let's all press "commit" button!  


I have three options:  


让我们按下"Commit!"按钮  
我们都按''Commit!''按钮  
我们所有人都来按''commit遵守''按钮！  


Which is better?
If you mean a button that appears on a screen, it is better to say "点击（click）..." 


  现在，让我们点击“Commit”。


I would rather omit "键" or "按钮" in the above sentence. 

按钮 normally refers to actual buttons that you can press by hand，such as the on/off button on your TV or computer. 

键 can be used when you talk about keyboards, remote control and so on.

If you are talking about an actual button, your first translation appears to be the most natural one.