Just finished the RS tour in Paris . You are in for a treat! The area around the Hotel Londres Eiffel has tons of restaurants and cafes of all kinds. Cafe Constant is great, but I’m guessing that there will be other options once you are there on the ground. Also, once you are there, the hotel staff and the tour guide might be of assistance.
You could really go anywhere in the city since the Metro is so easy to use and you will have a one-week pass. The Sacre Couer area also had many options. Another idea - Look at restaurants in large hotels. They often keep their restaurant open for there own guests since they have to eat somewhere! I have used this solution in the US.
On our tour, the guide handed out the tickets for the Seine cruise and let people choose to do it whenever they wanted - day, night , early, late, this day, that day. The tickets are actually good for almost two years. So just ask him for the ticket to use at a different time if the group cruise interferes with a special dinner.
In our group, we had three solos traveling alone, a set of sisters, a set of best friends, and several friendly couples, gay and straight. I was one of the solos and never found myself without companionship for meals or free time. I went out with various groups of 2 to 6 people. So it’s unlikely that you will be wandering around on your own (unless you want to as I did one day.)
Have a wonderful trip! Wait till you see how Paris is decked out for Christmas!