"You will not grab me, but I will come. Can we make sail for Barcelona?"
I forgot that there should be some sort of language barrier. The kid can speak Catalan and Arabic, the pirates are speaking Arabic but can manage Catalan.
Hand wave that.
"We are making for Sardinia sweetheart. And this ain't the time to get argumentative. I'm saving your skin, and protecting our back from any informants. Abducting you is far more merciful than killing you. So get up on board peacefully and I will see to it that you are treated well. Fight with me, and I'll toss you down below for the crew to pass around.
Get my drift?"
Your options are to fight or cooperate. If you fight, you might be able to get away, though it is doubtful you will be able to take Yanni and Yenni with you. Cooperate, and you may have etter opportunities down the road.
NOT trying to railroad you. If you can figure out a different solution, go for it. But I have laid the cards on the table 
"Indeed I do." Donna strides up onto the ship, then over to Yanni. "Well, looks like we are traveling now."
And in short order, the tiny pirate fleet is under way. And Donna is indeed treated well. She shares a cabin with Yanni and Yenni, you are given the good food and wine, and Donna receives and invitation from the captain to come dine with him. You can bring the kid as a chaperone to make sure everything is on the up and up.
The captain's name is Harlock :mrgreen:
Donna brings the kid along, and begins with the usual pleasantries before sliding into her real topic of concern. "So what plans are there after we make land?"
He offers you each some wine and dinner served is roast capon with some greens.
"I know a guy in Sardinia who is willing to join his ship to our fleet. It is but one, but larger than any of my current three. From there, I am thinking of raiding the shipping lanes of the Sea of Sardinia for a while. Recoup my losses after the crusaders sacked my stronghold on Ibiza. When strong enough, I plan to attack Ibiza. More for revenge, I don't expect to drive the Christians out by myself. But there is this one guy there, name of Raw Bert. Some sort of magician they say. I think he uses alchemy to create fire. I used to have a sorcerer as an ally, had his own little ship. This Raw Bert guy killed him and torched his ship. The other three sorcerers of the islands are hiding in fear of him. Him and the witch hunters employed by the Christians called "Flame Brethren". If I can take this Raw Bert out, I can convince the sorcerers to rally by my side and we can work on purging the lands of these Flaming Brothers.
But the main goal is money, as always. The Balearic Islands were by base of operations until the crusaders came. This situation is putting a serious crimp in my profits. And revenge. I want revenge."
Someone shouts to the captain, a ship has been sighted. One lone small ship. Easy pickings.
And, coincidentally (though Donna has no way of knowing), this is also the ship Isolde is one. Antoine's lady love from Hungary.
Oooh, pirates! 
Antoine is also, presumably, aboard, given the discussion in From Hungary. I'll assume they haven't spotted anything yet, and are just up on deck watching the shore slip by.
Donna sits quietly as the man rants, then when he is called away turns to Yanni "quests for revenge never end well, and if you dream of cooking somewhere more grand I have friends in Barecelona who can make that happen, and I am certain when they taste your pastries they will, but we need to get the three of us, yourself, your sister and I, off this boat and somewhere safer. Are you with me?"
Actually, I thought they took separate paths. Pause while I reread.
"Yes!"
"First off, are you familiar with this ship, or is this the first time you have been aboard?"
"Actually, this is the first time I have ever been on a ship. I puked my guts out earlier."
Yeah, you guys are not together. Not much of a storyhook if you are there already.
Okies. (A later post I made suggested Antoine would go back and accompany Isolde if she came by mundane means, but I'm sure he can be doing something else instead).
Or he could have gone back and been too late.
"Okay, then the first thing we need to do is find out where the smaller boats are, the dinghies or whatever they are called. If we wait for shore they are certain to keep an eye out. Also make sure your sister is with us, that is not a conversation we need to be having at the last moment."
Yanni is sure his sister Yenni is just as concerned about their uncle as he is. He was too old and got left behind. He will go talk to her in private, and returns confirming she is down with your plan.
"Right now we pretty much have freedom of the ship, we need to find the dinghy, then meet up after dinner." Does anyone have private rooms and what phase is the moon?
The captain decides to put the siblings in one cabin together, no guard. Donna is given a private room.
Whatever you are planning, just before leaving her room, Donna hears a knock on her door.
The captain is outside, a bit drunk.
[color=green]Donna my dear, I brought a bottle of wine. Ha ve a drink with me. His voice has a heavy suggestion of amorous intention.
"Captain, please come inside, make yourself at home, I just need to make a quick trip to the head then I will join you."
If he does as she suggests Donna will slip outside and lock her own cabin from the outside before meeting up with the others.
Well played 
Yes indeed, the captain had a lock put on your door, an impediment you would have discovered had you tried to slip out as you planned. As it is, you manage to confuse the captain with your confusing excuse (there is no "head", this is the age of the chamberpot).
So you lock the captain in, and he is to drunk to do anything about it. He falls asleep waiting for you. You realize that there will likely be a similar lock on the siblings' door.
I also need a stealth or guile roll. the deck is bustling with night crew as they track and pace the merchant vessel (mentioned earlier). They plan to strike at dawn, 6 hours or so from now.