Your children will also be learning values by watching you. If you keep the extra change when the cashier gives you too much, if you brag about cheating on your income taxes, if you're disrespectful to your spouse or parent, you children will literally copy your actions. Look for teaching moments with your children. Tell them that you've given the correct change back, although you could have kept it, because it's important to be fair and honest. Explain that you may have differences with your spouse or mother, but that you're willing to discuss and compromise with the people you love.
Life is an exciting story to preschoolers.
They don't yet refer to parents' discussions as lectures. They love to listen to you and feel your undivided attention. You have wonderful opportunities to teach good values and to help children distinguish between right and wrong. Remember that preschoolers are very literal and concrete in their thinking. The nuances and ambiguities may need to wait until they're a little older.