Advice on where to go

Going in July with a 7 year old. Flying in to Olbia, flying out from Cagliari. My plan was so stay in San Teodoro for 6 nights to visit all the nice beaches on the north/north east and then 1 night in Cagliari for our flight back.

Would it be worth splitting the trip into two parts? San Teodoro AND Alghero? We fancied having a walk around Alghero town and a day at La Pelosa beach.

San Teodoro 6 nights - Cagliari 1 night

Or

San Teodoro 4 nights - Alghero 1 nights - Cagliari 1 night