J R,
From the standpoint of enforceability and uniformity of fairness, the "no alcohol at all" rule that scottrc talked about is best. This puts things in their simplest and most understandable form. No alcohol allowed - period. That goes for everybody; pilots, spotters, spectators and anybody else. No muss, no fuss, no "misunderstandings".
We can argue forever about how much is too much, whether or not it's "family oriented", freedom to do or not, etc,etc,etc. That's not the point here. We're trying to make a rule that is the easiest to enforce, easiest to understand and contains the fewest liability risks. This is it.
You can enjoy your after-flight libations at any nearby tavern after the flying day is done, if you so desire.

papermache