Our family of 5 just spent 17 days on Oahu in Waimanalo. It was truly the best vacation we have ever had.
We rented part of a house, listed as Rena's Best Beach, which was incredibly clean and close to the beach. 100 yards or so is all it took to get to this incredible beach.
The water is aqua, the sand is golden, the waves are great for boogie boarding, and the beach was almost vacant during the week. We went in November so it was the beginning of winter. We did encounter a few cloudy or rainy days but we simply drove over to Ko Olina (to the lagoons there) or Waikiki and enjoyed the sunshine that is more prevalent there. Our 11 year old son is less certain of himself in the waves at Waimanalo so enjoyed the time at Ko Olina and Waikiki.
The quiet pace in Waimanalo creates a relaxation unobtainable in Waikiki.
There is a McDonald's, Jack-in-the-Box, L&L Hawaiian Drive-In, a Bakery which had warm glazed doughnuts in the morning, a drive-in called Kenekes (great steak fries!), a 7-eleven, and a few other commercial businesses in town. No large scale shopping, but who needs it when you have Waikiki to go to for any tourist gifts you could desire.
My husband, myself, and our 3 boys ages 11-17 all loved this area. We'd go there again in a heartbeat and hope to return in the future.