Chapter 3: Level 2 dungeon

You should expect that based on PHB chapter 15 glass would have AC 13 and 5-27 HP depending on how fragile it is made by design (I have exact number listed in the module). It is quite easy to break for a martial character using a weapon
Once any player choose one 6 six objects and announce their their PC breaking it - I will either explain what events it would trigger or just narrate that glass breaks, no roll required if it triggers nothing (and if it does we will most probably be rolling initiative).

If player what his PC to check wall for the hidden doors player need to choose 5 feet wide wall segment and roll perception check. Player could repeat that roll for either same or other segment as much time as he desire, but DM will increase DC for discovering doors every time player rolls a dice regardless of the result. A long rest and a secret door discovery resets the penalty to 0.

Alternatively - instead of wall segment you could pick an object (such as table) to try to find mechanisms hidden within. You still do the perception roll and I still increase DC for you if the were nothing to to find or you fail your roll.