Be very intentional about influencing your children toward the Lord when they are in your home. Deuteronomy 6 says to model God's values to your kids and impress them on their hearts. You must be diligent in this. Intentionally prepare them for the types of influence they will face at the other house. Be respectful about the people in their life but help your children have a plan. How are they going to manage whatever they are exposed to? Finally, pray constantly for them while they are there.