Dear Shellie,
First of all, you are to be commended for being so sensitive with your Primary children and in considering their needs.
Second of all, families can be together forever. That is the reality for which we all strive.
Third, none of us is perfect. Therefore, we need the Savior's path to attain the promises given.
Fourth, we can only be responsible for personal choices, not the choices of others (as hard as that is to adjust to in this life!).
So in summary, I would teach the doctrine, letting the children know that Jesus loves them and wants them to have a happy family forever. He wants them to choose the right and be a "sunbeam" for others. Also, teach them that others (perhaps even those in their own family) need help remembering these things. Promise them what the prophets have promised throughout the ages: those who love Jesus and who try to follow him *will* be helped in this life and rewarded in the next.
Remind all the children that we are to help everyone in our families, and that sometimes things don't make sense right away, but God promises that for those who love him, he will turn all things to their good (Romans 8:28).
Finally, you will receive guidance as you pray for guidance. It sounds like you are a wonderful teacher. :-)
For additional idea, you may want to visit Robin Salazar's site "Teaching LDS" for some great ideas. Here's the link:
http://www.bellaonline.com/site/teachinglds Happy teaching!
C.S. Bezas
LDS Host
http://www.bellaonline.com/site/lds BellaOnline.com