Name/nickname question

Trista
Ok so we are due in October and we don't know what we are having. We've had a boys name picked out forever and we are struggling with a girls name. I finally got my husband to agree on one (Emersyn) but after I did that I started thinking about nicknames. I don't mind the common nicknames (Em, Emmy) except we have family members who already use these names. We are thinking about going with that name and then for a nickname we are thinking about using the first initial of the first and middle name (EL pronounced Elle) as the nickname or Emer. Then on the announcement we would put the nickname on there in parenthesis. So my question is; how likely will people use/stick with the nickname we've picked rather than using the more common ones?