I can sort of nip around the edges of your questions, as my son and I visited Sardinia in February, 2008 to meet up with some families he had met in Italy on a prior trip.
We flew RyanAir into Alghero, stayed a night and bussed south to Cagliari. We stayed there 3 nights and flew out, again with Ryan.
The hotel we found in Alghero was through Ryan's site. Alma Di Alghero. A 3*. Comfortable, but not over-rated. We were well treated there though. The city itself has a lot of interesting history and we wished we had had more time to explore it. We took a bus from the airport, and the driver was very helpful in pointing out our hotel and giving us directions to get to it (it was dark out and not right on his route).
We learned a hard lesson on the bus from Alghero to Cagliari - the Sunday schedule is much abbreviated. Got there eventually.
At the bus stop in central Cagliari, about a block away across a little city park, is a tourist information place. We just asked for a hotel there and they found us one. Again, nothing fancy, 3*, but right downtown and convenient for seeing the sights there. A wonderful museum, pizza at a department store restaurant that was really great, and lots of history. Very interesting to just wander around the city.
Wine everywhere was uniformly excellent, yet very reasonably priced. People were helpful.
We had an incredible visit with the friends.
Really can't help you with a hotel appropriate for a honeymoon, but I'd guess somebody here will step up to the plate.
Romelle