Kauai is the most beautiful of the Hawaiian Islands, and Poipu is Kauai's best beach area. There are several fine resorts along the stretch of coast constituting Poipu, but Marriott's Waiohai Beach Club has the best beach and its accommodations are ideally suited for families or a couple of couples. The sand, surfing and snorkling are all right there (as well as a great pool). The waves hitting the beach are gentle (surfing takes place out past the reef). Even at high tide, there is plenty of sand. There is no better location for a beach vacation.
Each room is a suite consisting of two fully contained king size bedrooms. One has its own bathroom with a separate shower and jetted tub. The other adjoins a full bathroom with a shower in the tub and a surprisingly large capacity stacked washer and dryer. Access to this bathroom is also possible from the front hallway but the door of course can be locked ensuring privacy. This bedroom also has a fold out sofa bed. Each bedroom has its own flat screen TV, closet and large window. Between the bedrooms is a full kitchen, dining area, and sitting area with another fold out sofa bed and a large flat screen TV. This opens out to a patio with table and chairs.
There is plenty of grassy, open space at the resort for sunbathing, much of it close to the water's edge. The resort has a coffee shop and small store, but it is a short walk to some of the best restaurants on the island -- Roy's or Keoki's Paradise at Poipu Shopping Village or an even shorter walk to Brennecke's, Plantation Gardens or Red Salt. Less than a mile farther (best to drive) The Shops at Kukui'ula house Merriman's, Lappert's Ice Cream and other good restaurants. Don't miss the Gourmet Farmer's Market there on Wednesdays 4-6 pm (be sure to hit the Right Slice pie booth).
Underground parking is plentiful at the Waiohai resort. One of my favorite jogs (be sure to start early before it gets too hot) is from the resort beach path to Hoone Road, past Brennecke's and the Poipu Beach Park, turning left on Pe'e Road. Continue past several hotels and a larger resort (whose name I can't recall), right down a wide paved path through a large grassy area, and then along the Hyatt Resort beach path and back.
Monk seals beach themselves on Waiohai's beach. Snorkeling, I have seen every kind of Hawaiian fish, turtles, and even a large eagle ray. See if you can find the peace sign made of rocks out there in the middle of the cove. You always will want to return to Waiohai.