I'm tempted to say two words: Financial aid (or maybe 'student loan').

From what I'm hearing from financial gurus it's better to build your nest egg rather than fund their post-graduate education unless you're 100% positive they will be paying for your entire retirement. If they go off and raise a family, you're not guaranteed they'll pony up (pardon the pun) when you would like to sail off into the sunset...

There are way more options to fund education than retirement...