Priscilla,
I am sorry for the unexpected closures but I was in Paris last month with my children and we enjoyed several museums that are not as well known but the collections were equally amazing(and they were less expensive).
The Musee d'Arte Moderne- not only does the permanent collection include several Impressionist works by Raoul Dufy, Matisse(the actual La Danse ballet backdrop), Picasso, Delaunay... but the temporary exhibit of Albert Marquet is wonderful. Crowds are lighter and the cost is much lower-permanent collections free, I think I only paid for myself for the Marquet exhibit(12euro) students free. You feel like you have the place almost to yourself.
Centre Pompidou- the building is crazy looking but the permanent collection includes Picassos, Matisse, Picasso, Mondrian, Kandinsky and the Gerard Fromager temporary exhibit was wonderful. We paid about 18euro total for myself and 2 students, the views from the balconies and rooftop are amazing. DO NOT wait in line to go to the top of Notre Dame when you can go straight to this rooftop and take photos with Notre Dame in the background.
And lastly, the Institut du Monde Arab has a fascinating temporary exhibit on Oriental(east and far east) gardens that we enjoyed and the architecture of the building is fascinating. The rooftop views from this left bank spot further down the river are wonderful.
I have blogged about each of these if you need more details.
I know you will find plenty to enjoy- There is never enough time in Paris.
www.elizabethmcgriff.com