Wife and I are sailing out of Norfolk September 2. We were also worried about the parking situation since we will be driving from Richmond. I found this information on the Sept 2 Magic board. I am pretty sure you can drop off your bags as soon as you enter the parking lot. Hope this helps.
https://nauticus.org/cruise-parking-directions/
I think/hope Carnival has improved the situation after the horrible problems they had last year, with cars being broken into, rammed, and major delays... the lot holds 1200 cars so should be ample considering a lot of people ride together, get dropped off, fly in, etc. I haven't heard of the lot filling.
We will be driving in the morning of from Raleigh. First time out of Norfolk for us.