I have even thought about counseling with a Christian counselor before we even setting a date to try and tackle this issue before it causes harm or serious divide.
It is VITAL that you three get on the same page BEFORE getting married. If it can't be resolved to everyone's satisfaction, then you may have to call the marriage off.
I have no other advice to give since I've never been in your situation, and the situation is complex. Professional Christian counseling is probably your best bet.