It would just count towards the lifetime gift exemption. A bit more paperwork but no tax bill as far as I know. Until your parents expect to leave $10.9M or more in their estate when they die, won't produce any taxes later either. Before you even had to do paperwork, it may well be possible for each of your parents to give $14,000 each to you and to your wife (so $56,000 total transferred between the two married couples in a single year without stating to use any of the $11M lifetime limit.*).
Are you comfortable with the situation you're getting yourself into? Three generations under one roof, technically all in your name. Lots of money changing hands, presumably with lots of implied conditions and expectations. None of my business either way.
*http://www.elderlawanswers.com/will-you-owe-a-gift-tax-this-year-6069