Suggestions for what to do in Paris 1 day before and 2 days after Paris Tour

I did that tour last Sept/Oct and it was wonderful! I also arrived from London the afternoon before the tour started.

May 2 is a Monday so there are lots of museums that are closed and in addition it is a 1st Monday of the month so the Musee Armee (Army Museum) is also closed then. I would go to the Cluny Museum which is open on Mondays and something else perhaps in the neighborhood of your hotel. Which hotel are you staying in for your tour?

On the back end, I would make sure you do the Marmottan Museum which is the museum with many Monets. You will have just been to Giverny and this collection will probably be interesting to you.

If you are interested in Asian art, the Guimet is also very good but without huge crowds.

Neither of these are off the beaten track altho they are smaller and don't draw the same kind of crowds as some of the other museums.

Somewhat off the beaten track is this walk in the 7th of Art Nouveau. This one is very convenient if your tour hotel is one of the ones Rick uses in the 7th.

http://www.parisperfect.com/blog/2011/03/art-nouveau-7th-arrondissement/

Or I also enjoyed walking thru a string of the covered passageways which are now filled with shops and restaurants. Very fun! I have one of the laminated Streetwise Maps of Paris and when I started looking for the addresses of them on there realized they were all marked in blue denoting a pedestrian walkway, so pretty easy to navigate. Here is a link to a few of them:

http://www.aviewoncities.com/paris/passages.htm

Have an excellent time! This is a fun tour with a variety of very interesting things to see. Do make sure you do Leonardo Da Vinci's home in Amboise on your free afternoon there.

Unless things have changed, if you want to do the Eiffel Tower you will need to do that on your own, so that might be a good choice on those dates.

If you want an interesting museum that is "off the beaten path" go to the Pasteur Museum at the Pasteur Institute. You can read the info online about days, times. You will need to have your passport with you for security clearance. Extremely interesting, not just from the viewpoint of science, but also because there is a perfectly preserved apartment from the past that you get to explore.
You show up for the tour and anyone else who has shown up is on it with you. We had maybe 10 people in our tour group and the guide graciously spoke in both French (everyone else) and English (to include my sister and myself). This is a true "Europe through the backdoor" experience and location.

We also really enjoyed renting bikes. Very easy to set up an online account and then choose a bike from the many Velib bike racks all over Paris. Riding along the river was especially fun.

Some things you probably missed on the tour: St. Denis (the most overlooked yowza site in Paris -- well just over the border but on the metro)

https://janettravels.wordpress.com/2010/10/26/confronting-mortality-at-st-denis/
The Nissim Camondo Museum and the Marmottan are both often overlooked museums worth including.

Doing your own self guided walking tour -- lots of books with suggestions for those is fun. And if you spent a lot of time in Paris then a day trip would make sense -- to Auvers sur Oise, or Chartres or Crecy la Chapelle or Conflans Sainte Honorine or any one of a couple dozen small towns with charm within an hour or so of Paris.

The Pasteur Museum is currently closed to all except organised groups, due to heightened security following the November 13th Paris mass murders.