Thanks! After posting I worked up the nerve and called (I've little experience calling FR from US), managed to secure the reservation at Grotte Font-de-Gaume for late morning of day following our arrival.
I guess we'll rent a car at Limoges as it seems easy enough to get to from Paris, large enough to have some car deals, and my wife wants a peek at the local craft (enamel painted copper, etc.). Really don't want to cope with renting a car in a larger city or making a big drive after flying all night and transiting Paris to Gare Austerlitz.
Trying to decide if staying in Sarlat-la-Canéda is good enough or should move around some. Do want to see Rocamadour upon advice of a waiter who likened it to Mont-St-Michel.
Any other suggestions for things to see in Black Perigord ?
merci,
benzguy80