Thanks Lyndzies. Your post made me smile.
Extremely good points, fille. I have wondered the same thing, but I haven't thought about it in a while due to the distractions of ttc. I thought about what it might be like to use the format used on "The L Word" (Mama B, Mama T), but I wonder if that's too much like "Mom 1 and Mom 2." Also, our initials don't roll off the tongue as well as theirs. I called my mom "Mommy" as a little kid but switched to "Mom" when I was still pretty young - definitely less than 10.
With regard to your question about what other people do, my only knowledge of another couple's mom-names is a sad one: the kids called the non-bio mom "auntie," and I believe this was to avoid discrimination/violence when the kids were growing up in the 1970s and 80s. I don't know if the adult kids still call her that. Fortunately, that's not really necessary today.
If/when I conceive, I don't know what I and my wife will be called, but I want us both to be Mom! What about using the English "mum"? Seems like a possibility, because you would hear the difference within your family, but outsiders would pretty much hear it as "mom."
I had a young teen at my church with a mommy and mama. She generally said "mom" in conversation but it was usually clear based on context and if she needed to clarify she would say "my mom" and then the mom's name. To her moms I would hear them both getting called mom, but once again it was always obvious in context AND I did hear her call them mommy and mama on occasion.
Truth be told, I could never remember who'd given birth to her--which was always a nice reminder to me how little gestation can end up mattering...