Can you consume alcohol in the back of a slide-in camper?

I am about to embark on my annual family road trip to my relatives in Illinois. we are driving out there in the back of a slide-in pickup truck camper. My father is going to be driving, and seeing as My three siblings and myself are of age, we were wondering whether we could partake in alcoholic libations while in transit.
I have heard various things as far as drinking in an RV is concerned, but I am not sure whether there is a distinction made between an RV and a slide in camper. I know that as far as seat belt laws are concerned, they are treated slightly different than either an RV or a passenger vehicle.
I understand that this sort of thing varys by state so I am trying to gather info on each state we are passing through
NY: no clue
PA: no clue
IN: Driver only open container laws… so heck yeah.
IL: designated as a mobile home, so maybe

Is there anyone out there that can help me make this year an exceptionally merry Christmas?