Baby Step 4 in Dave Ramsey’s bestselling book and system, The Total Money Makeover, is to invest 15% of your gross pay in good growth stock mutual funds. While it is just a rule of thumb, he recommends 15% of your gross pay and not your net pay which means that you calculate the investment before taxes.
Show your kids this amazing comparison chart to illustrate the power of starting early when it comes to investing. Then open a Roth IRA as soon as they earn W2 income. (See: http://blog.famzoo.com/2011/04/pave-road-to-retirement-for-your.html)