Can we pair one remote with Mac, and one remote with AppleTV in the same room?
Yes. Follow the instructions in this Apple Support article for Macs or this other article for Apple TV.

Essentially, the procedure is this:


  Pairing your remote with your Mac:
  
  
  Log in on your Mac as an Admin user.
  Get very close to your Mac (about 3 or 4 inches away).
  Point the remote at the infrared sensor on the front of your Mac.
  Press and hold the Menu and Next/Fast-forward buttons simultaneously on the remote for 5 seconds.
  Your Apple Remote is now paired with your computer. You should see a chain-link style lock appear in the center of your screen for a moment.
  





  To pair your Apple TV with a remote:
  
  
  Choose Settings > General > Remotes from the main Apple TV menu.
  Choose Pair Apple Remote.