HI, I dated my husband as a non mormon and i had no intention of joining the church, it was many years later that I was moved to join. We were actually married by a mormon bishop. With our children we allow it to be thier choice when they are old enough if they want to date mormon or non mormon, we have eight and we 4 that date mormon exclusive and 4 that will consider someone outside the church. The only thing I would say is respect who they are and take time to listen to why they practice what they practice. one of our daughters may marry a non memeber however he does go to church with her and does respect her values and helps her uphold them , and says if they marry and have kids he will support them in the LDS church, my seventeen year old is dating a baptist miniters son. They have been great and they alternate churches to go together and are celebrating similiarities and repsectfully understanding the differences but the 2 churches are creating a mixer to allow these kids a chance to get to know each other and build bridges over rivers of ignorance and prejudices... so to answer your question, it can be done successfully if everyone involved is committed to it knowing there can and will be hurdles.