DH and I went for our honeymoon in August, and our flight didn't get into MCO until nearly midnight. We were checked into the hotel and in our room by 2:00 AM. If I recall, our luggage arrived in our room very early in the morning. I was anxious as to whether it would arrive before we woke up, but it was not a problem. We were planning to wake up around 6:30, and I think the bags arrived around 4:00 AM.
I had the same worry you did, but we just packed enough (toothbrushes, facewash, PJ's) to get us to the morning, and the luggage arrived no problem. If I recall correctly, they have 4-5 hours to deliver your luggage to your room.
You can also pick it up yourself and load it onto the Magical Express to be sure it arrives with you.