Avoiding alcohol is always the safest, however, moderate alcohol consumption (up to 1 drink/day) is NOT known to be harmful to the infant, especially if you wait 2 hours to breastfeed. Drinking alcoholic beverages is not an indication to stop breastfeeding; however, consuming more than one drink per day is not recommended (CDC).
Breastfeed just before you leave for the party (opposed to drinking as you are about to breastfeed)-This will give you more time between your drink and the feeding to give your body time to eliminate the alcohol.
If you plan to drink heavily, prepare expressed milk in bottles ahead of time for someone sober to give your baby. Wait at least 4-5 hours after the last drink or better yet, until you are feeling sober to breastfeed. This will allow time for your body to clear the alcohol from your bloodstream and from your milk. If you can safely (and legally) drive a car without concern of a DUI, you are most likely sober enough to breastfeed your baby (from verywellfamily.com).
And, this is just a saying..., and I am not saying this..., but have heard it said, if you can find your baby, then you can breastfeed your baby. (Uhhh... I guess that depends how far away your baby is, how familiar you are with your surroundings, your coordination, and if you are wearing HEELS!!).
Don’t bother to pump and dump your milk since alcohol stays in your milk as long as it does in your bloodstream. So, don't waste money on those breastmilk alcohol strips because your brain/functioning will tell you when you have sobered up. If you are feeling overly full, pump to relieve pressure/fullness, but chances are if you can figure out how to find your pump parts and pump your milk without spilling, you may be sober enough to breastfeed.
Stay hydrated with water to keep your supply up! Alcohol causes a decreased ability to let down and dehydration, the opposite of what a nursing mother needs! Yes, carry that big jug around with you and own it proud mama! No sense in losing the supply you worked so hard for.
NEVER co-sleep with your baby if you have been drinking alcohol. Make sure you have safe sleeping and childcare arrangements for your baby.