On the Fantasy, when we attended the afternoon "Sea Ya Real Soon" (on
Castaway Cay day) all the main characters and princesses were there, with no lines. There were no photographers, so we took our own pics or had CMs take pics of all of us, but we literally got pics with about 12 characters in 15 mins.
Besides that, we waited 5-10 mins for most character meets. Our longest lines were for the princess greet, which is now ticketed, and also the pirate night characters.
Ticketed meets are very easy and quick.
We also bumped into a lot of characters on the ship, and they would stop for pics or to dance and play with the kids. Once we bumped into Rapunzel, and she took my 4 year old's hand and walked her to the kids club with me. Also, there are many character events in the kids clubs. If you have kids and leave them in the clubs, they are bound to have encounters in there.
And yes, on embarkation day, there are plenty of characters waiting in the port and atrium... the port had long lines, the atrium did not.
There are also meets on Castaway Cay, and there weren't lines for us with those.