We love Waikiki - its a very different vibe than any other place we visited in Hawaii. Lots of shopping, dining options, nightlife and all in walking distance. It did remind us of South Beach with a bustling area plopped on the beachfront, but we enjoyed it nonetheless. What we also liked about it is that there were TONS of bus tours and organized tours offered from the area, with pickups at the various hotels. It makes for an easy way to see the island or go to places like Diamond Head and Pearl Harbor, where parking can be challenges. I think I mentioned up-thread that our bus tours to Pearl Harbor and Diamond Head worked out very well - it was nice to let the pros worry about the logistics. And we had just two people - you have a few more.
As far as the ages go, every place we went was family friendly. We saw kids on the beach, and the beach is great for people watching. I would say the area is primarily for walking, just in case your parents have mobility issues. There are also double decker trolleys that go up and down the strip that are easy and cheap to use.
1) You mentioned Turtle Bay, which is a gorgeous resort with great pools. It's on the north shore technically, but its more located between Haleiwa and the windward side. My favorite part of the north shore was Haleiwa, and Turtle Bay is about a 20 minute drive from there. You'd definitely want a car at Turtle Bay.
2) We loved Kailua, which is on the east/windward side. The beaches there were the nicest we saw our whole trip. It has more of a laidback vibe in that area. I think this would be a good area to stay in, but again, I'd have a car.
3) My comments on Waikiki are above, although Hilton Hawaiian Village wouldn't be my choice. Its a beautiful resort but at the far end of the strip so its longer walks to most places. There is a trolley stop nearby. We stayed at the Marriott Waikiki and thought it was the perfect location.
4) This one would be my vote. We stayed in Lihue near the airport. We thought Kauai was the most exotic of the islands we visited, with the most natural beauty and least commercialization. The Na Pali Coast was my favorite thing of the whole trip, and I highly recommend Capt. Andy's sunset dinner cruise. It was awesome. We did a helicopter tour as well which went over Waimea Canyon and the coast, and while we enjoyed it, it was definitely a splurge. We had 3 days there and did and saw everything we wanted, with time for relaxing at our resort as well. I would recommend booking the inter-island flight for either early morning or late night. We did lose about a half a day by flying mid-day. Had we gone early or late, we would have had more of a full day. The flights are very short - 30-40 minutes.