lucky you.
take good walking shoes.
i suggest a hotel in Paris. we have had a few bad experiences wth airbnb in Paris.
Metro is great.
Versailles is a great day trip - with excellent picnic opportunities.
Musee d'Orsay in Paris. Rodin, hang out in Le Marais. Napolean's tomb and accompanying museum. Pere La Chaise - a great place to wander - see Jim Morrison's gravesite, Sacre Coeur,
we once took a trip to Monet's garden - it was worth it.
took a high speed train to Avignon - rented a motorcycle - went exploring - it was friggin sublime.
on and on it goes ......
wish we had taken a train to Rome, while in Florence.
did take the train to Sienna - Sienna worth a trip (Hotel Certosa di Maggiano - highly recommended) San Giminana? mostly a tourist trap feel to it. YMMV.