Flight
*to search both Parisian airports at the same time, type "PAR" On Alternative Airlines, there is a handy button to search for only refundable flights. Expedia offers refundable credit. Most airlines are now offering a fully-refundable ticket due to COVID. Check out their website and be sure to read the fine print. Lufthansa also has an Economy Flex option which included full reimbursement :)
Rental Car
Rental Cars is a great site for comparing prices and also has great, affordable options. Your itinerary from Paris to Pleneuf-Val-Andre where both families and many guests will be staying requires 30 euros for tolls. Calculate 35 euros for gas. Mappy is a great website to calculate everything you need! It is a 4.5 hour drive
Train
The oui.sncf is the main website that everyone uses in France. Alternatively, you can book your train on trainline.com. Both offer e-tickets that you can scan directly on your phone :) Depending on which Airbnb you choose, you will either want to choose Paris --> Lamballe or Paris --> Saint Malo, or even Paris --> Saint Brieuc It is approximately a 2.5 hour drive. If you are planning on taking a train and need picked, we will organize this with people who have cars in the area :)
House Or Rental
The general area we will be in is called the "Côtes-d'Armor". Click on the link I've given to jump directly to the filtered search. Here is an 8 person Airbnb that you could share with other guests for example that would cost $125 per person for a one-week stay: https://www.airbnb.com/rooms/6572909?adults=8&check_in=2021-09-29&check_out=2021-10-06&source_impression_id=p3_1611315520_iAfRs21dUUcLDwho There are many other options but I suggest looking between Saint Brieuc and Saint Malo if you want to be close to everybody.
Travel Note
January 2021: We are currently waiting for the French border to re-open. Updates to be posted here! A negative test within 72 hours before the time of ARRIVAL in Paris is currently required.