We know how hard is to get small children quiet during Sacrament Meeting. You also want to emphasize the importance of listening to the speakers. One great idea is having a bag of sweets or any sort of treat (doesn't have to be food related if you are worried about cavities ) and let your kids count how many times they hear the word Jesus Christ in the talks. For every time they hear that word, they earn a treat. It is great because they have to focus on listening to the talks to get the treat. Hope the idea is helpful.