First, pas clair que is present in CNRTL, but not pas clair si (as far as I can tell - please correct me if I missed it). In terms of frequency of use in writing, it looks like pas clair si is becoming more and more common. Interestingly, pas clair que was overwhelmingly dominant in the 19th century, but pas clair si is becoming more and more used in the second half of the 20th century. Overall pas clair que is still about twice as frequent as pas clair si today. But still not mentioned in CNRTL as far as I could tell (?)
Back to your sentences, the following sounds ok to me:
Il/Ce n'est pas clair si la fête va avoir lieu chez Pierre ou chez Marie.
Il/Ce n'est pas clair si la fête va avoir lieu chez Pierre (ou non).
I don't think the number of options plays any role here, but ait IMHO doesn't work at all. In the second example I put (ou non) in parentheses to indicate that it is optional.
Maybe the following would be even more natural, although not strictly equivalent (this il n'est pas clair is a bit awkward):
Je ne sais pas si la fête va avoir lieu chez Pierre (ou non).