Sounds promising, don't you think?
Yes, sounds like a very nice trip. I like these small cities in Northern Italy, almost each of them has its own special charm. Bergamo is nice, the medieval city centre is located on a hill, completely surrounded by defensive walls and connected with the lower city by a funicular. And the Certosa di Pavia is worth a visit, with its impressive renaissance facade and the two cloisters. There are already a lot of monasteries on the list and thus a nomination probably has little chance, but 10 or 15 years ago Pavia certainly would have got an inscription.
I visited the four sites near Capo di Ponte. The main site is the Parco Nazionale delle Incisioni Rupestri Naquane with about 100 engraved rocks. It is signposted from Capo di Ponte. Here you can find a useful map of the park, the numbering of the rocks is a bit confusing:http://www.parcoincisioni.capodiponte.beniculturali.it/index.php?it/137/luogo-e-sede
The park Ceto/Cimbergo/Paspardo is a few kilometres south of Capo di Ponte (also signposted). You have to park the car at the archaeological museum in Nadro, and then walk about 15 minutes uphill (if I remember correctly). There are a lower number of rocks than in Narquane and they are spread over a wider area, but I enjoyed to hike through the forest and climb on the rocks. However, it was in summer, in december it might be less enjoyable. Masso di Cemmo is in Capo di Ponte opposite to a small museum, but there are only two large rocks. A few hundred metres uphill is the Parco Communale Seradina-Bardolina, the engravings are very similar to those in Naquane.
If you are not a big fan of rock art and your time is limited, Naquane would be sufficient to get an impression of this WHS.
And if you find a little time for diner: the region around Bergamo and Brescia is well known for Polenta.