First France Trip - Initial Itinerary

This looks to me like a wonderful itinerary. You're giving yourselves a fair amount of variety without trying to cram in too much. Honestly I can't think of anything to criticize, even as devil's advocate. You've probably read RS description of the Loire chateaux. Staying in the Loire 3 nights gives you 2 days of touring, so you'll want to choose 2 chateaux per day that are, on each day, fairly near one another.

Especially to be applauded is your return to Paris the night before your departure. Many people make the mistake of thinking they'll just get up early and drive or take a train to their departure city, which IMO is asking for a lot of extra stress because you never know if there could be a traffic delay or a train disruption.

Itinerary looks fine; we would opt for more time in Paris and perhaps save one of the other stops for another trip -- but those are very personal decisions and I wouldn't second guess your selections. As for CDG hotels, there are many choices. We used the Marriott and found it to be excellent: clean, modern rooms; reliable shuttle service; terrific breakfast buffet; and immediately adjacent to the surprisingly charming village of Roissy-en-France that somehow survived the development of the enormous airport 1/2 a mile away. (Several other hotels on the same road offer similar access to Roissy.) Our base in Provence was L'Isle sur la Sorgue, but we enjoyed St. Remy one morning and my wife would put it at the top of the list were we to return. She was greatly impressed by the sight of a shop-keeper scrubbing the sidewalk in front of his store with hot soap/water. The self-guided walking tour of viewpoints of several of Chagall's popular paintings is another highlight of St. Remy. May is a brilliant time to visit -- we did so in 2016 (Normandy; Provence; Paris) and encountered manageable crowds and generally good weather.

I like your planned itinerary. But have you considered flying home from an airport closer to your Provence locale, instead of going all the way back to Paris? You could add an extra day to your Paris stay. You could spend most of your last day in Provence instead of on the train; then in the evening stay in Marseille and fly out from there the next day. Or, better yet, book a late flight and go to Marseille that morning.

We stayed near L'Isle Sur la Sorgue as well. It was a great home base for exploring the area.

Thanks so much for your responses everyone. I appreciate the input!

Keep in mind that your first (partial) day in Paris may not be worth much if you don't sleep on the overnight flight. If that turns out to be the case you'll have just two days in Paris.