My parents in law objected. My wife was smart, told them we were coming anyways and negleced to tell me anything. 
Therefore I acted normally & they were polite, if reserved. Luckily my future sister-in-law was there and we could talk normally.
Do you have siblings? It helps if there is someone else there you can interact ‘normally’.
Diego…when was the last time you had any girlfriend anywhere where you could tell the parents you pulled her at a disco? Normal rules and sense apply. 
