They have to clear all the passengers out from the last cruise and get the ship ready for the new arrivals so it takes time. I doubt they will start boarding before 12 noon if that is what is stated, any delays arriving into port and clearing the ship could mean an even later start. The best idea would be to aim for a 1.30/2 arrival even then you will still need to go through the usual checks befoe boarding, but I would have thought on this arrival time you should in your cabin no later than 3 p.m. There will be some 2,800 passengers to board with no doubt over 6,000+ pieces of luggage so it is quite and exercise. The cases will not likely be there by then it could be a little bit longer before they are delivered to your cabin. So if you have a small case like the type you take on the plane then have your 2 year olds necessities in this with some for yourselves then you can take it on board with you. This is a rough guide but even if you are in your cabin by 3 there will be a muster drill 30 mins before the ship leaves port and then you will be heading for 1st dinner no doubt, so a tight schudule for the first day then after that all calm and relaxing !!