A lot depends on where you stay and what you do while in Paris.
I really think that if you can stay at the Marriott CE you will NOT have a problem.
The Marriott is right on CE and you should not have a problem getting around or enjoying the sights close by. You could do a lot of travel by metro but the steps in and out of the stations could be a problem. My experience is when you get on the BIg Red or Green bus in front of the hotel you can sit on the open air top deck all day, take pictures and not walk at all!