Planning Your Time
A great advantage to exploring this region is that all its major monuments are within a half-day's drive from Paris, or less if you take the trains that run to many of the towns. The catch is that most of those rail lines connect Ile communities with Paris—not, in general, with neighboring towns of the region. Thus, it may be easier to plan on "touring" the Ile in a series of side trips from Paris, rather than expecting to travel through it in clockwise fashion (which, of course, can be easily done if you have a car).
Threading the western half of the Ile, the first tour heads southwest from Paris to Versailles and Chartres, turns northwest along the Seine to Monet's Giverny, and returns to Paris after visiting Vincent van Gogh's Auvers. Exploring the eastern half of the Ile, the second tour picks up east of the Oise Valley in glamorous Chantilly, then detours east to Senlis, and finishes up southward by heading to Disneyland Paris, Vaux-le-Vicomte, and Fontainebleau.
For a stimulating mix of pomp, nature, and spirituality, we suggest your three priorities should be Versailles, Giverny, and Chartres.