I'll take a shot though I've not cruised from Jacksonville
It actually begins before you park - you should be able to drive to an area and drop off your luggage. Be sure everything is tagged. You will see it again outside your stateroom several hours later. Anything you may want to have over the next few hours (swim suit, meds, etc.) is in your carry on.
After you park you will proceed to the terminal. There you will verify the information on your Fun Pass, arrange payment for on board expenses and have your picture taken for your sign & sail care (the picture is not on the card - but is checked each time you embark & disembark). The Sign & Sail is your room key and your on-board money (for the most part - not sure about the casino).
As you embark you will have a group photo taken that you will have the chance to purchase later.
Once you actually embark you will plug your S&S card into the little bing bong machine that security uses to be sure you are aboard and that you are you. You can go check out your stateroom and the rest of the ship. The buffet on the Lido deck will be open, so you can start eating right away.
There will be a life boat drill very close to sail away time, and then there may be a sail away party on the Lido.
You will have a good time for several days
The last night you will be provided customs forms and need to pack your suit cases and have them out by midnight. Sometime overnight they will be taken down to the hold. You will be given new luggage tags that will have a number that indicates your order of disembarkation. If you are driving you will probably have a high number, so you can relax and enjoy your last morning aboard.
After the ship clears customs they will be begin calling groups by number to disembark. This keeps the customs lines shorter and makes it easier to find your bags.
Alternately you can drag all your bags off yourself, but I doubt your mother & aunt would be too interested in that.