Day 1 (half-day) - Montmartre, Eiffel Tower at night
Day 2 - Historic Paris walk, Louvre, Arc de Triomphe at night
Day 3 - Musee d'Orsay, Orangerie (in and out here, really just want to see the Waterlilies), Invalides
Sadly, we only have 2.5 days before we move on to the Loire...although we will have another half day at the end of our trip if there's something we absolutely need to see.