While Giverny is a great place to visit, I wouldn't do it on the day I arrived after a transatlantic flight. You'll be jet lagged and possibly sleep deprived. You will have to check into your hotel and drop your bags before you do anything else. Even with an early morning arrival, by the time you have cleared immigration and gotten to the hotel, it will be late morning already.
As long as it isn't storming, get outside for a few hours. Pick one or 2 things to do that aren't on the tour itinerary. Perhaps one of the walks in Rick's book. His historic Paris walk is usually the first thing we do. Have a nice lunch at a cafe. Stroll along the Seine. Maybe take a river cruise ( highly recommend doing this after dark). Then have an early supper and get to bed at a decent hour so you're rested for the next day.