Ciao Mary, welcome to our forum!
So you're giving Tuscany/Bologna/CT a week and then Sardinia or Sicily for the second week, right?
Any time in Rome in between? Make sure to give yourself some time there too!
In Tuscany, I would suggest staying
central in the region so that drives are not too long: the area between Siena and Florence is ideal for drives to
Pisa,
Lucca,
Siena,
San Gimignano, around
Chianti while you can explore southern Tuscany (the
Val d'Orcia essentially) as you drive up from Rome.
For places of where to stay, start searching for Chianti here:
http://www.tuscanyaccommodation.com/chianti/
If you want to stop while driving up in Val d'Orcia, take a look here:
http://www.tuscanyaccommodation.com/val-d-orcia/
I assume you don't plan to stay put in one place for the entire week, especially if you want to fit in Bologna/Modena and Cinque Terre as part of that week so for that reason you should plan maybe for 2 or 3 nights in different places.
Take a look at the itineraries we have on here for ideas of what to see:
Itineraries in Tuscany - We have one for 5 days:
https://www.discovertuscany.com/itin...n-tuscany.html
because if you include CT and Bologna/Modena, then you really won't have a full week in Tuscany.
As for whether Sardinia or Sicily..... that's hard since they are quite different. Being August, consider both will be quite crowded as they are very popular beach destinations. Sardinia is considered more "wild" in that there is less development, but many parts of Sicily are like that too. Consider that from Rome, getting to both will be easier by ferry as opposed to driving and you can plan to do it overnight so that you don't "waste" a day of sightseeing. I can't recommend one over the other because I think it depends on what you want to do and see and where you are from to just suggest a place that might be more different than what you're used to or have seen already. I think overall Sicily has more "sights" and Sardinia is more for hanging out at the beach, at least that's my impression.
If you want beach time, you could also consider
Elba! Much closer to Tuscany and Rome ;-).