The idea behind not nursing while you are still feeling the effects from drinking is from a safety of handling baby standpoint...as in difficulty walking or standing, etc., although you may have a raging headache later in the day, breastfeeding would be fine. Although, obviously if you are very intoxicated, your blood alcohol level is likely fairly high.
True, the levels will decrease from your milk just as they will from your blood, but again, at his age, he will not metabolise the alcohol as quickly as if he were older.
Basically, if you have a glass or two you don't need to pump and dump....you could feed him yourself at his next feed. Space each drink out over a period of time and you have even less of a concern. If you know you are going to have more, have some expressed ahead of time for baby to have while you are drinking, then give it a few hours before feeding baby at the breast again if you are feeling up to it. As was said, you may need to pump before that time just to avoid discomfort.
You can leave the breastmilk at room temp if you are just going to a wedding for the day....if you wanted to be sure, or thought you might be gone for the better part of the day...especially if the room temp is fairly warm, you can just pop it into a cooler bag or the fridge.