It is very easy to rent a luxury car in the city. There are many limousine companies in Paris who provide their services in the city. I know europe limousine service. The rental price is affordable. You can rent a car for a few hours or for a whole day with a driver. You will be driven around the major attractions and make the necessary stops. You do not have to walk.
When I come to a new place, I prefer to walk and see different sights. It's better than seeing the city through the windows of a car. A couple of times I have found local guides who privately give tours. That was really cool.