The best tax lesson you can pass on to the kids? Show by example. Let them sit in on a few minutes of your tax return preparation. Give them a look at what income can be considered a tax liability and how other wages can help them move closer to a bigger refund.
And perhaps give them a real-life lesson in how tax works by asking them to divide up their money like Uncle Sam would. Ask them if it's better to put aside a little "tax" for every dollar they earn or if they would prefer getting a big bill at the end of the year. Ask them for suggestions about things they might be able to get tax "breaks" on, just like Mom and Dad get a bit back from the government for having kids or buying a house.