Leave the baby at 2 months???

It's my baby sisters 21st birthday party at a nightclub here in San Diego the first weekend in December. My baby is due October 1st. Any mommies have any advice on how they felt when their baby was just 2 months? Was there a time you needed to leave them for a siblings birthday? Or someone specific who was close to you? I feel like I'm NOT going to want to leave or even be away from my baby. But I also don't want my sister to think I'm making excuses. Because she's been told by other mommy friends of ours that mommies do leave their newborns for certain events. They don't like to, but that it's possibly (obviously) but I'm the type of person who doesn't even care for nightclubs anymore.😞 any advice from anyone?