It turned out fine, although there was confusion at the beginning. The driver (who picked us up at our hotel) understood that the package included a city tour and a tour of the Orsay Museum. The guide was delayed (about 30 minutes) due to problems with the trains, so we sat in the car for quite a while before the museum tour started at about 9:30 am. The guide was very knowledgeable about the museum. At about 11:30 am, I asked about the plan (for lunch and for the city tour). She seemed confused by my question, but we went to a restaurant in the museum and ordered meals. However, while we waited to be served, she was on the phone, and when she came back, she told me that the driver had another appointment. She seemed not to understand that the package included the city tour, and that the whole thing was supposed to last about 3 hours. We cancelled our lunch order and started walking toward the museum entrance. After some thought, she suggested that we could have lunch (in another place) and then do a brief tour by taxi. So that's what we did, and it was just fine. The experience was just great, and I think we probably got a much longer tour because of the confusion. My suggestion is that you discuss the plan with the guide before beginning in order to avoid the awkwardness.