I don't remember calling home for Mother's Day from my mission in the late 1970's. Of course I was in Germany, so a call home was not cheap, and my parents were not in the US for Mother's Day (they were living in Africa where my dad was on a work assignment), but I don't even remember there being a discussion of whether it could happen or not.
My brother, who served his mission 7 years before me, sent my mother roses on Mother's Day. He had called our local florist in our home town to order the flowers rather than using FTD.
Still, we're thrilled to have a chance to hear our missionary daughter's voice (and to see her, too -- I guess we'll be Skyping for half of the hour we're allotted for the call).
We assume she'll be as prepared as the elders at this link.
Happy Mother's Day!