Paris to Bordeaux things to do along the way??

You have a couple options. You can take a direct train to Blois and rent a car there to explore the Loire Valley or take a direct train to Colmar and rent a car there to explore the Alsace wine region.

I vote for the Loire Valley……we saw the gardens of Villandry, Cheonceau and Cheverny……the Seine flood kept us from seeing Chambord but will try and see it again this spring on our trip back…….we stay at Hotel les Minimes in Amboise…..loved it so we will be going back to the same hotel….Villandry took our breath away! Rent a car….you will want to have your own in the Loire Valley. Amboise is a charming town to base out of……I think you will love the Loire Valley!

Alsace is nice but certainly not on the way from Paris to Bordeaux.

You can take a look at ViaMichelin.com to see what it recommends for driving routes. Certainly the train will be faster than driving, but you have plenty of time on the way down to make some interesting stops. ViaMichelin proposes three different routes between Paris and Bordeaux. I don't know where your cruise ends up; I'm thinking it probably isn't Bordeaux. Therefore, I'm not going to address the return trip (when you have much less time in any case); you might want to take a train back to Paris.

If you zoom way in on the Michelin map, any especially scenic stretches of road will be highlighted in green.

One of the routes (the most central one) runs through Orlans, Tours, Poitiers and Saintes. I've been to the last two and liked them. Poitiers has a lovely historic district and some very old churches.

The western route runs through Chartres, Le Mans, Saumur and Saintes. I haven't been to the first three, but I understand from posts here that they are all worthwhile.

The eastern route runs through Orleans then takes you not terribly far from Bourges (where I haven't been) and Limoges. I really enjoyed Limoges--very pretty historic center and good decorative-art museums.

The Loire valley is a very good idea.
I do not know how long you wish to allow to Paris itself, but with 5-6 days on the road, you can travel from Paris, to Chartres, Loire Valley, and perhaps a stop in Poitiers en route to Bordeaux.
On the way back, I would take the train, 1 night isn't enough for a proper road trip.

OK i ship opened up from Lyon to Avignon as originally planned. Fly in to Paris then head to Lyon Viking to Avignon then fly out of Nice. 5 days in Paris beforehand and 5 days on the French Rivera somewhere after the river cruise. So it ends up between Bordeaux or Lyon-Avignon? We can hit the Loire Valley on route to Lyon?

Sorry but your experience is helpful.

The part of the Loire Valley with all the famous palaces is not really on the way from Paris to Lyon, but if it is a high priority, it is not that bad of a detour either.

You could even do this without a car if you are happy just getting a quick taste of the Loire area and don't want to shortchange Paris either. You could take the train from Paris to Chenonceaux via Tours (Saint Pierre des Corps), stay there for the night to visit Chenonceau castle, then take the direct train to Lyon from Chenonceaux (yes there is such a thing!!).