Leave more than enough milk plus your baby's comfort items (favorite toy or blanket, music, etc). Tell your caretaker (yaya, grandparent, etc) to send you updates every 30 minutes. But more than anything, after all your preps, make sure to enjoy the event and tell yourself that you need that break. Being a relaxed, healthy, happy person makes you a better mom!
Start spending some time without your baby months before the event proper so that the baby will get use to being without you.