I recommend Breakas Beach as it has no kids under 16, a pool and is on a sand beach, has tour desk etc. The beach out front can be rough with exposed coral at low tide and further out has a popular surf break.
Another great one is Erakor Island. It has nice bungalows just steps from flat water at the entrance to the first lagoon, a sand beach, good beginner snorkelling out front, over water restaurant, kayaks, tour desk etc. Because its an island you don't get traffic noise. The ferry takes about 3 minutes to get to the wharf on the mainland (about 5 mins closer to town than Breakas) where you can jump on a local bus for $2 pp. Check them out in the Hotels link at the top of this page.