In my experience most non-monogamous relationships start with either 1) two open-minded people in a monogamous relationship exploring the *idea* of experiences with other people or 2) people already comfortable with non-monogomy finding each other. I would caution against trying to make this work with two women who haven’t expressed any interest in it especially when you seem to be the sole beneficiary.
Question for you— would you be down with each of them having additional boyfriends?