I learned that if I have Shemitta wine which has kedushat shvi'it (home-made or from an "Otzar Beit Din"), I must take it outside the house and abandon it ("Hefker") on erev Pesach before 3 people. Can the Abandoning be before 3 women or must they be men? Can they be relatives?

The Kaf HaChaim says that all 3 should be men, but R. Abba-Shaul and many others disagree and say that one of the 3 can be a woman or a relative, but the other 2 must be men, and not related to the wine-owner nor to the other kosher witness (they can be just distant cousins...) for they serve as legal halachic witnesses. Also they cannot be your wife or children.