Best spots for a 15 days trip to Sardinia and Sicily

We are planing my wife and I a 2 weeks trip to Sardinia (around 8 days) and Sicily (5-6 days)

We chose Sardinia for the beaches, so we would like to know what are the best beaches you have visited there ? What are the best parts of the island to stay in ? Is 8 days too much ?

For Sicily we’d like to explore more historic side of the island, as well as some countryside tourism (like experiencing a winery) what are your recommendations for that ?