Of all the beaches we went to during our stay at Nusa Lembongan, the children enjoyed Mushroom Beach the most. Not because the beach was nice, but because they got to ride the banana boat several times.
Coconut Beach was where we stayed the most during our visit to Nusa Lembongan. Mostly because it was so close to Tenang Villas where we stayed. But also because it was less busy. Mushroom Bay is a much bigger beach, and more sandy. But at the same time more difficult to take a swim in, due to the heavy traffic of boats coming and going. But the kids loved it. Due to the banana boat trips they got to take.
If you are going to Nusa Lembongan, you should definitely make a trip over to Mushroom Bay. If you find it too busy, you can always walk or swim around the end, and find your self laying down on what feels like a hidden and secluded beach. Just you and the sand. But make sure to make a visit to Coconut Beach also. And Dream Beach. You ought to have at least one meal at The Deck and make time to walk across the Yellow Bridge. It is worth the trip.
Read more about what to do, and where to go during your stay at Nusa Lembongan at Sunset Travellers.