Welcome to the LL Community. Sounds like you are planning an interesting trip in August. You chose an excellent hotel. The Lutecia is wonderful and right int he middle of things. Don't miss to visit the department store Bon Marche, one of the oldest, just a few feet from the Lutecia, and especially have a look at the Grand Epicerie food store, one of the most impressive ones in Paris.
As to your guided tour of the Louvre, I suggest you take your Louvre tour on Sunday, since every first of the month, the Louvre and most other museums are free of charge. To avoid the crowds, I suggest you enter by the Port de Lion which is a small, little known, entrance into one of the wings by the Seine, close to the Tuilleries. You rarely find a crowd there, and it gets you right up to the Mona Lise, which surely you don't want to miss. Once you get down to the main information desk you can get audio guides that cover the entire museum.
As for walking tours, I suggest www.ClassicWalksParis.com, or www.paris-walks.com . From it you can chose a number of walking tours which might interest you. If you are sportive, I suggest you rent one of the bicycles from many of the velib, www.velib.paris.fr, stations to tour the city on your own which can be a lot of fun, or take a bike tour of Paris offered by www.fattirebiketoursparis.com.
I also suggest, you check out my many posts on Paris under various threads. You should find plenty of information there. If you like any more specific info, please let me know. Have fun