If you've never been to Paris, and all you want to do is see the highlights and soak up some atmosphere, 9 days is plenty of time, even counting the fact that you'll generally lose 24 hours due to jet lag and the departure day.

There is an awful lot to see and do other than the usual tourist stuff, but I think first time visitors would be quite happy - and probably exhausted - doing just that. It's hard work being a tourist in Paris, loads of walking, stairs, waiting around in endless lines, trying to communicate...take it easy the first visit.

I think Bayeux deserves more than 1 day - you should plan to stay overnight, if you're really interested in the beaches.
Chartres takes more time than just half a day.
Versailles - you should definitely plan on one whole day.
August is brutal - crowds are enormous, trains don't always run as they should (breakdowns are frequent) and it's hot.
I would maybe re-think Chartres, unless you're really interested in this cathedral.