K.C.
I think Kristen said it best! Have a "welcome home baby" or "meet the baby" party you can host. Call your mom-in-law for a list of contacts and addresses for invitations - I bet that would get her moving!!! Then she'll know that if she doesn't do it, you will :)
I think it may even be better to have a "shower" after the birth than before. By 3 months of age, you have a better idea of what you do need and don't need, so the registry will be easier. And the best part is that everybody gets to see the twins at the party.
You are a very special woman to move so far from friends and family to be near your husbands family. I think that shows alot of courage and dedication to your own, newly formed, family.