Vacuum cleaner in the apartments and some renovation will make it a 4 star residence.
Sea: shallow entrance for small kids. Nice evening animation for all kids irrelevant of their language. WiFi: free around the beach area. Capo d'Orso (Cape of the Bear) heights visit is a must - stunning views.
Beach (sand): 2 sunbeds and a parasol 15 eur whole day, 8 eur from 13.00; you can use you own parasol and beach towels, but it's busy on weekends.
Apartments: well equipped, but I missed a spatula to make pancakes and omelette. Recommend to take with you small necessities as salt and spices; small bottles of dish washing liquid and all-purpose cleaner; kitchen towels, sponge, rubber gloves - enough for your stay and it will all fit in your hand luggage; earplugs, for in case your neighbours are noisy. Don't forget a sweat coat and a raincoat. All the rest (including sun/rain umbrellas) you can buy at EuroSpin, Palau, - it's the cheapest and has a nice choice. Porto Mannu is well located to visit northeast Sardinia by car: we travelled to the neighbouring Santa Tereza Gallura, Porto Rotondo, Porto Cervo, Arzachena, Cannigione, Costa Paradiso. And after visiting all these places all of our group decided that Porto Mannu was the best place to stay. One week in eastnorth is enough: try out Stintino and surroundings even if your airport is Olbia. Olbia-Alghero route is quite relaxed. Orosei Bay (Olbia) has nice beaches, but with deep sea entrance, and the nicest beaches could be mostly reached by buying full-day boat trips, not for small kids.