Day (or a few days) excursions from Paris

I see that Chartres is not included in the BOP tour. Easy short train ride from Paris to see its cathedral.

What time of year ? I would recommend Giverny, but not if it’s when it is closed !

Amsterdam is 3 hours away by bullet train. And of course London.

Another vote for London, 2.5 hours away via the Eurostar, city center to city center. London also works as a long day trip, taking an early train over and a late one back. Food and drink is allowed aboard. Eurostar.com or seat61.com for helpful tips on all rail travel across Europe.

Haven’t been yet, but have heard good things about Chantilly, just a bit to the north of Paris - beautiful chateau (now a museum) and gardens, horse museum with live demonstrations, lace, Chantilly cream….

Another vote for Chartres. Easy train ride. The cathedral & hotel is a short walk from train station. We spent 2 nights in this charming town and enjoyed the evening Light Show on the Cathedral facade- magical! One night would suffice if you want to do other excursions. We had a tour of the gorgeous Cathedral with famed historian Malcolm Miller. We went to a stained glass demonstration next to the Cathedral. Walkable picturesque town, and wonderful cuisine as well.
https://www.travelawaits.com/2548814/how-to-spend-a-day-in-chartres-france/

For a few days consider WWII sites in Normandy, Mont Saint-Michel, Loire Valley, Route du Vin in Alsace.

So many wonderful ideas! Thank you all...

Visiting Normandy would educate your girls on WWII. Especially since they’re at the age when it’s taught in school.

What do the girls want to do?

I could see countering the time in Paris with some time in the French countryside, so they really feel immersed in France.

But, if they’re interested in the big cities, then some days in London would be memorable.

We spent several weeks in Paris once or twice a year and always do a side trip -- from 2 to 5 nights. These days, that is by train as my husband can no longer drive and I don't want to. Some recent examples: Brittany -- 4 nights in St. Malo as a base and one night in Auray to see the neolithic sites; two nights in Angers and 3 in Nantes; earlier with car Normady: 1 night Mont St Michel, 2 nights Bayeux and two nights Honfleur -- with the full days used for the beaches and for Etretat. This year we did two nights in Lyon which is an easy visit by TGV and a walkable city. Here are some of our day trips from Paris
https://janettravels.wordpress.com/category/day-trips-from-paris/
You can see pictures from Etretat, Honfleur, Bayeux, St. Malo, Neolithic sites, Mont St. Michel, and Nantes on the same site to get an idea of some things easy to do as short side trips from Paris.

https://search.ricksteves.com/?button=&date_range=2y&filter=Travel+Forum&query=chartres+rouen+chantilly&utf8=%E2%9C%93

If you're staying in France, then I suggest the Loire valley using Blois as the base to stay at.

So many wonderful ideas. Lots to sort through here. Thank you for your generosity everyone.

The tour is really 5 1/2 days. Another option is to stay in Paris and do a day trip. I am going 2 days early before my tour and staying an additional 6 nights after. I plan on doing one or two day trips....maybe Rouen.