I have 2 small drawstring bags, one filled with Legos and one filled with junk (broken Popsicle sticks, small rocks, broken hunks of concrete, twigs, etc.)
I have 2 children each come to the front of the room, in view of all, and build a house out of their materials, so we can then compare the different "houses".
Our good, carefully thought out decisions are like the Legos. If we make a good choices, we have a strong, healthy, safe future and life. If we make poor choices, our building materials are poor, and we end up with a shaky future that won't take more than one shake to send it toppling to the ground.
Questions to ask: Which house do you want to live in? How can you make choices that will result in strong testimony?
Choose three or four children to come up to the front and try to build a house out of the contents of the first box. (Obviously it will not work very well) Then choose three or four children and have them come up and try to build a house out of the contents of the second box. (Hopefully, if the kids cooperate, it will work much better)
This can lead into a discussion about how we use the very best to build the House of the Lord. You could show pictures of various rooms inside the temples to give them an idea. You might also be able to use the song, "The Wise Man and the Foolish Man" or "I love to see the temple." Source: http://www.eprimary.dk/ - (visit the Primary Object lessons section)