Activity: Luxembourg Garden and Seine Cruise. Metro Stop: St. Sulpice. Cost: Luxembourg Garden is free, the Seine Cruise is €9 adult, €7 kids, cheaper to book online ahead of time. Hours: Always open, changing of the guard at 11 am.
Luxembourg Garden. This perfectly Parisian park has it all, from tennis courts to cafes and lots of big toys. Try to find the large chess game. Also see if you can catch the puppet shows in the southwest corner of the park. We loved spending time in the little playgrounds (which sometimes have a small surcharge, but they are so clean and nice I didn’t mind paying it!). Best to just show up to Luxembourg and wander about. You’ll happen on some beautiful spots! We particularly enjoyed the area behind Palais du Luxembourg. Our kid liked throwing small pebbles into the pond back there.
A fun and surprisingly affordable thing to do after exploring the garden is to cruise the Seine with Vedettes du Pont Neuf. The cruise leaves from Point Neuf (where the Historic Paris walk ends).