John,
Sorry for the confusion about the time. Jay is right. They man the gate starting at 0600 but there's an "after hours box" where you can pay even when it's not manned. The ramps are open for launch 24/7, so you can launch the boat at anytime. If you're planning to get there before 6 (which is probably a good idea on Memorial Day weekend), you'll still have to wait until the Marina store opens (at 6) to get the hang tag saying you're going to be there for more than just the day.
By the way, the price isn't per day. Just the initial cost to get in (6 bucks/adult) and that's it. So if it's just you and Connie, it'll be 12.00 for the weekend to launch, recover and park.
One last thing. They also have around 6 finger piers that you can tie up to. They're on a "first come first served" basis, so if you wanted to get there REALLY early, you could launch and have a place to tie up. Years ago I did that with a buddy on a crabbing trip. We got there at around 2 or 3 in the morning to beat the traffic, launched the boat, tied up and went back to sleep for a few hours.
Cappy
Liberty Call