Bucket List Trip in Sardinia, Italy in September

Just wanted to suggest that the driving in the north may not be too worrisome. I would not suggest you drive in the east (Cala Gonone and, mountains, and Orientale Sarda) because it was definitely intense to me, but in the north it was no different than driving anywhere, and you may save money by doing so (and costs were appreciably higher in the north overall). I am less familiar with the south. There are boat excursions galore where ever you end up, so once you pick your base, you may not need any private drivers to get to beaches.
I thought about Sardinia a long time, and there are many many choices, so dive in--it take a while to narrow down your options. Pinpoint the ideal itinerary first (DK and Lonely Planet have newer guides), then see what driving assistance you need and if modifications are needed.

We spent 18 days and drove all the way around Sardinia, including two side-trips off mainland Sardinia to smaller islands (one in the northeast, one in the southwest). We moved pretty quickly (in retrospect, I'd now say a little too quickly). If you want to do both the north and south of Sardinia (and both are wonderful) I think 2 weeks is not quite going to be enough - I would either add some extra days (3 weeks would be great) or resign yourself to missing out on a lot as you blow past other great things that are neither in the far north or the far south.

I think you really need your own car on Sardinia, unless you are going to just stay at some resort the whole time (which would be a shame). Even to get out to a lovely beach, it'll be difficult without a car.

I found the driving pretty easy just about everywhere, everywhere we went, all around (do be extra careful if you drive at night: the only really challenging driving I encountered was through the mountains just inland of the east side, where we experienced a spectacular and very intense storm with torrential downpours, hail and lots of thunder and lightning). Of course, don't drive into the old historic centers of cities, the streets become impossible and there are ZTLs.

Sardinia is spectacular (shhhhh...). September is an ideal time to go. You will be gobsmacked.