If I know that I am going to have a big night of eating and or drinking, but don't want to gain any weight, am I best counteracting the excess calories by exercising earlier in the same day, or is it more effective to have a big work out the following morning?
One big night of eating and drinking wont have such a big effect on your body but it can trigger unwanted desires like me and ice cream. The best is to eat healthy or eat small amounts like finger foods on a spaced out time limit and drink a low calorie wine, like red or dry white, keep out the sugars in sodas. The best is to work out in the morning which will kick start your day and flush out all the junk throughout the day from last nights eating and drinking.
Exercise more the day after...you'll have more food/calories in your system, which will give you more energy to continue working out (kind of like carb-loading before a marathon). This way, your metabolism will stay higher longer thus allowing you to at least burn a little more than if you exercised pre-party day.
If you are gonna have a heavy night out, here are a couple of suggestions; do not work out in the morning after, especially if you are hungover. You'll end up feeling like crap and most likely mess up the recovering metabolism. In extreme scenarios you might end up fainting in a moment of intense workout (has happened to a friend of mine, he must have had a pretty bad experience as he's not had alcohol since that event).
I'd suggest working out a couple of hours before you get in your party mood, you'll probably feel hungry when you start eating, but will soon get full especially if you drink a bunch of water after the training (which you probably should). I can not give a reference about whether or not it's a proven strategy, but all my friends who are into serious workout regimes skip the day after a party and continue with a heavy session the 2nd day.
Besides as the others have mentioned, you will not gain much weight, if you do gain any at all, after a single night.
Hope it helps