will be staying at Marriot near Disneyland Paris on May 16-23, and will be going back to Paris on numerous occasions. its our first trip to Paris.
A possible ticket solution would be Navigo Jour day pass for arrival day (Saturday, May 16), single-use tickets for Sunday or another Navigo Jour day pass if needed, then a Navigo Week pass for Monday - Saturday (May 23). This will probably be your cheapest / easiest solution.
Navigo week passes only start to work on Monday, hence the need for some other tickets/pass for the first Saturday/Sunday.