First of all, I’m sorry to hear about your dad’s health. Like was stated above, drinking won’t help it, or help you navigate your feelings about it. I’d venture to guess in fact that it’s important to approach this time with clarity and focus.
Which makes me feel like I have to put this out there: you could skip the trip to Mexico. Your sobriety is really important, and a booze fest is hard for any recovering addict, never mind one who’s father is ailing. I’m sure your wife and MIL would understand. Consider it.