I'm confused why there was do much dilemma over how much Xanatos knew/what to tell him?
He's got a shit ton of intrigue and is one of those "a hand in every pot/knows what's going on almost everywhere" kinda guys... when I first saw the vote I thought to myself he probably already knows so it doesn't really matter beyond how he perceives the manner in which we tell him.
Which, still important but I digress.
As far as which of the options to take... I'm really tempted to say we should take the Xanatos one. Janna's our employee, so we can always contact her, ya know, contacts later. Have her reach out, if nothing else.
And we can always hunt down a potion maker on our own time (which the option seems to suggest).
But when it comes to Xanatos... it's not every day that we'll have the chance to ask him something like this and have him likely to give an answer. And it's possible he might even go so far as to introduce us, or even recommend us to someone that we wouldn't otherwise be able to access/gain an audience with.
So, yeah, I definitely think we should take up Xanatos' option.