If you want to do a picnic lunch in the Champs de Mars at the Eiffel Tower, I would, without a doubt, go to the Rue Cler market, which is very close in the 7th, and one of our favorite market streets in Paris.

I have been to the catacombs and have mixed feelings about it. There is a long undergroound walk prior to reaching the bones and once you arrive, there are indeed human bones everywhere. These bones are made into walls, forming a maze, many with artistic bone designs. It is interesting at first but it wears off fast. We did not have a tour guide and would probably recommend one as I assume there must be more to it than just transporting all these bones from around Paris to one place. Do it if you have time to kill (no pun intended) but I wouldn't make it a priority.