Hi whiplashed_mom,
You might look over at the suggested reading list on the Building Healthy Relationships Board, here is the link:
https://bpdfamily.com/message_board/index.php?topic=56209.0 to get some info and develop talking points with your children.
Off the top of my head I would say that it begins with being healthy, well grounded, having and defending boundaries, and a positive outlook on life in general for each of your children. Codependents, those with low self esteem, and rescuers will tend to gravitate towards needy people who will accept them and then you have problems x2.
Bowens' Family Systems suggests that we often choose partners that are our equal in regards to emotional maturity. The higher level of emotional maturity that we achieve the higher level of emotionally mature mate we will seek. You might spend some time reading Bowen and his theories and see if there are any nuggets of good info.
Hope some of this info helps give you a starting point from which to begin to coach your kids on choosing life partners. Of course the greatest teacher is watching our parents' relationship over the years. Modeling a healthy, mature, kind, and caring marriage for our kids is powerful.
lbj