3 year old. PLEASE READ?

My son is 3 and wll be getting dental work done in a couple weeks. Im very nervous because he has never taking any pain meds but tylenol. They told me they would be giving him Valium (so he would be relaxed), laughing gas and tramadol. Is this way to much medicine for a 3 year old? Has any one else been through this with their kids? They assured me they would be watching him closely on the montior but im still scared. He is also allergic to motrin. Please help with my fears.