I'm with Chani and TC...walk, walk, walk!
Near the Louvre are some very cool Covered Passages that you can walk thru. Many are filled with shops and restaurants, so it's great if the day is wet. Here are some links:
http://www.theguardian.com/travel/2012/mar/02/paris-hidden-passages-shopping-shops
http://www.fodors.com/world/europe/france/paris/experiences/pariss-covered-arcades-53789250
http://www.aviewoncities.com/paris/passages.htm
If you happen to have a Streetwise laminated map of Paris, you can see them on there. They are outlined in blue. Otherwise I can pick some of them out on googlemaps but you have to know where to look. From the Louvre, go north to where you see Galerie Vivienne.
If any of you are interested in Art Nouveau, do this walk after you go see the Eiffel Tower.
http://www.parisperfect.com/blog/2011/03/art-nouveau-7th-arrondissement/
Last time I was in Paris I tried to see how many times I could pick out the Eiffel Tower from various places in Paris. It's amazing how often you can see it! My favorite is how many times you can look out the windows at the Louvre and get a glimpse.
I'm old so these may not appeal to you but there is plenty to do!
Also, get Rick's Paris guide book (does well on an iPad) and do some of his walks in there.
Have a wonderful, wonderful time!
PS Really, you need to go to the Eiffel Tower your first weekend. Not to go up in it, but get off at Ecole Militaire metro stop. Walk the couple of blocks to the Champs de Mars then along it to the Eiffel Tower (being very wary of any young women with petitions that ask you if you speak English or are pretending to be deaf and mute....just hold on to your purses and walk on).
https://en.wikipedia.org/wiki/Champ_de_Mars