Sounds like you guys have a plan. lol. Make sure you got to Cafe Du Monde for the beignets. They are the best. There is one in the Riverwalk Shopping Center, but if you want the experience of sitting out in the quarter, then go for it.
The ship usually leaves port around 4:30 or so. If this is your fiance (husband)'s first time, you will want to be somewhere on deck to see her leave and go down the river.
There generally isn't that much of a wait to get on the ship in the morning. When you arrive to the terminal and check in, they give you zone cards. When they start boarding, they will call you by zones to get on. I think in April, we waited probably an hour to get on board after checking in. Last October, when she was right out of drydock, we waited almost 2 1/2 hours, I think.