Carennac , Curemont, Autoire, all that area is well worth visiting, but it is only about 50 minutes from Sarlat where the OP will be staying. It can be an easy day trip out of Sarlat. Rita, maybe you can lengthen your stay in Sarlat to a week, and cover Carennac/Autoire/Loubressac as daytrip(s).
This way you keep down the number of times you have to pack-schlep-unpack.
As for the Lot, the area along the Lot/Célé river is a little further south and has its own concentration of beautiful villages - smaller, much less visited but just as beautiful as the villages in Dordogne.
Beautiful villages and towns that leap to mind:
- St Martin de Vers,
- Marcilhac sur Célé,
- Espagnac Ste Eulalie
- Calvignac
- St Cirq Lapopie
- Figeac.
Excellent bastide market town: Villefranche de Rouergue (market thursday morning).
You can - must - also visit the prehistoric cave Pech Merle.
I recommend staying in st Cirq Lapopie not only for its beauty, but because it can be so overrun during the day. If you stay in the village and can be there at dawn and at dusk when no one else is around, the experience is out of this world. Only two hotels. I have stayed at both: the Sombral and Pelissaria, both good, esp the latter.
The old château in St Cirq has been made into a b&b. I have not stayed there but can vouch for its beauty in and out.
Here is the link.
Another place I can recommend is
this b&b in Tour de Faure, in front of St Cirq. It is a Karen Brown favorite.
All that area between Cahors and Figeac along the Lot river would be what I would consider "the heart of the Lot region". It is about a two-hour drive from Sarlat.