You have a double whammy with your mom's dementia and your son. You won't regret spending time with your parents...my mother went downhill very quickly and passed away 2 years after we moved her to a nursing home.
I put my daughter's issues on the back burner during that time...she does not have substance addiction, but drinks heavily and I can see the progression. I sit on my tongue and withdraw after I give my unwanted statements.
have a safe trip.
your son is fortunate that he has a girlfriend, how much will she put up with?