I'll be passing through Paris from Gare du Nord to Gare du Lyon on May 2. I'll return to Paris on May 29 and stay until July 1, when I will need to get to CDG. I assume a monthly Decouverte Pass makes sense for June 1-June 30. Should I get an Easy Pass for the trip across town on May 2 and for the May 29-May 31 return? I think 10 trips should be enough for those days. Can a regular Easy Pass ticket be used to get to CDG on July 1? I hope all of that is clear. Thanks
A Navigo Easy Pass would make sense for covering the few days not covered by Navigo Decouverte, using a pack of ten Ticket t+ on the card.
You can add a Roissybus (Paris-CDG bus) ticket onto a Navigo Easy card, which travels from Opera in Paris and stops at all CDG Terminals. (You can't add any RER tickets onto a Navigo Easy.)
Another option is to add a Day Pass, 1-5 zone, onto a Navigo Easy and that will cover RER B trains to CDG in addition to Roissybus. This would make sense if you need to make several Metro/RER/bus trips during the day prior to making your way up to the airport.
Navigo Decouverte month pass is definitely the best option for June.