When is my actual due date?

Hello everyone I just had a quick question. I am a first time mom. I am currently 23 weeks and 5 days. My estimated due date is December 6. Unfortunately a lot of my family lives 4-5 hours away from me but they all want to be at the hospital when I give birth. Everyone keeps asking me around what day will I be having the baby so they can plan and take off for work. How do I explain to my family that I have no idea what day the baby is coming! He may come on my due date he may come 10 days late or 10 days early lol how am I supposed to know! I want all of my family at the hospital but of course it's hard for people to come to the hospital at the drop of a hat. How can I get a better idea of when my baby will arrive?