To be honest with you, the Vaux Le Vicomte castle is my favorite place to visit over Versailles. It indeed inspired the King of France after seeing it, to duplicate it ( albeit on a grander scale) with Versailles. I find the Vaux (Privately owned and thus better kept)to be less crowded with visitors and more magnificent in scale.
For children its a treat, as on weekends you can rent ( at the castle for 4 Euros) costumes so that they can dress up as Princes, princesses and Musketeers when touring the castle.