How about my somewhat less wordy plan, which unequivocally states why Ysilla is not in any danger, but also explains what fate would befall the Wildlings if they decide not to follow Bloodraven's guidance?
Gives away too much inconvenient information, and doesn't promise to fix it. Though that's the same flaws I find with Artemis's version, though his has mildly better infosec, due to brevity.
[] Plan Crake + Promises
-[] "To be perfectly honest my Lord? They would be beyond foolish to ask what would be beyond the
means or overruling the expectations of a young girl of a noble house not yet even flowered. What could a girl of her years yet do without personal power at her own command but for the ear of her Lord father? If it was beyond such means and they asked it anyway, foolish are they in the doing, then, since they would answer to her relatives and their allies."
-[] "Such open ended favors exchanged with strangers are
not what I would recommend any person make without desperation guiding them, but then anyone could have made such a promise not many years ago and without the eyes and ears of the Gods weighing heavily upon them. The world is closer to the stories of yore than it is to the one either of our fathers lived in, which is why I stress the importance of educating...
everyone, about the dangers that we face, both from men who dabble in sorcery, have the ears of gods, or whatever else ilk preys upon the misconceptions of mankind this day."
-[] "As to what can be done? I doubt fire and steel should be necessary to absolve her of the favor owed... but mere
words exchanged between they and I. I admit I am interested in what kind of person would even be interested in holding such a promise over the head of a child in her position. But beyond my curiosity I also have a
duty. The sister of my
friend, close in my council besides, has placed herself in a position that I feel she would not be in if I had only made contact with you sooner. But holding blame like packages to be weighted and passed around... it sounds pointless. Regardless, even if they hold such designs as you imagine upon her, I do not plan on leaving it to fester over your house, but will resolve it promptly now that I'm in the Vale. "
[X] Crake