Your check-in time is really in a sweet spot…people start arriving at 10, they generally start being admitted to the terminal about 10:30, and there is a crowd at that time. We've stood in long lines just to get in (through security) when it opened, yet the line seemed to evaporate behind us! They start boarding 11 ish or 11:30 ish, and often by 12 or 12:30 there is little wait. Even those with seemingly high boarding numbers are okay because before long they announce open boarding.
Although everyone wants to get on as soon as they can (I know we do), there is a relaxing feeling to letting the first couple of hours crowd duke it out and come on in around noon.
It's a sweet spot because not long after that the various Disney buses start arriving from the airport and resort, and they inject large groups of cruisers.
So, my advice would be there is no advantage to arriving earlier (you won't get an earlier boarding number, and if you are too early you might have to wait to get in). Your time is called "port arrival time" but that's a semantic distinction, since you are arriving to check in.
Arrive and check in about 11:45, it will likely be less crowded and comfortable, and you'll get on the ship in plenty of time to enjoy lunch and explore.