We have another week in our delightful 3 week stay in Paris. Any thoughts on the above question? All of your previous suggestions have been so helpful--thanks!

Depends on your interests--if they include art and gardens, then Giverny by all means. Chantilly is a splendid example of a "small" château, and the library is absolutely magnificnt.

Haven't been to Senlis and so can't comment on that one.

With the extra time you have, you might be able to do both Giverny and Chantilly as half-day trips.

chantilly and senlis could easily be done on one day trip - most Fodorites frown on this but it's possible as they are but a few miles apart. Monet's Gardens are closed on Mondays i believe. (Train to Vernon, then mini-buses or taxis or 3.5 mile walk from station - walk goes over an abandoned rail line along the Seine.) Vernon itself is a workaday unremarkable but not unpleasant town few people ever see when passing thru it to go to Giverny - a neat old village little changed on the outside since Monet and the Impressionists heyday.