Our church has discussion questions which are published each week in conjunction with the sermon. We also get questions for the family. I'm gonna try to throw out one each week which will hopefully be helpful in your family worship.
Spend some time coming up with 4-5 groups of choices you will ask your family to make. Find pictures of each item to display. These should be groups of 3 (possibly 2) items that include one item that is not desirable (i.e. a horse, a beautiful dog, and a very mangy cat; a fancy new car, a big new pick-up truck, and a wagon without wheels; a gallon of ice cream, a picnic spread, and a pile of rotten lettuce). Tell everyone they need to make a choice in each group of the item they would like most. When they finish, ask which ones they chose, and ask why no one chose the "yucky" items. Then Read Deut. 7:6-8 and Eph. 1:3-6 and teach your family about God's calling of His people and that He called no one because of what they looked like, or because they were so good, but so that His calling would be to the praise of the glory of His grace.