Maybe describe exactly what he's doing as he's drunk. I can imagine two reactions, from my own limited experience: total embarrassment and confusion, or hilarity. Oh, wait, three: fear. It depends on the situation. For me, my aunt was totally drunk and started coming onto my dad. I was so unbelievably embarrassed! But let's say it was another uncle, inebriated, and saying silly stuff in front of the family. That might be funny as long as the adults are there. On the other hand, I think of one incident when I was little, with a babysitter who took me out with her boyfriend in their no-door open top jeep, then to his apartment, where they started playing with fire. I don't think they were actually drunk, they were just being stupid teenagers, but in the absence of other responsible adults I was quite scared.
I think it can be really terrifying for small children when the adults around them suddenly fail to be responsible.
