Went there on spring break with the kids, using my 713 free week. Very crowded for the first 5 days, but the kids loved having an endless supply of friends at the pool. The ocean is warm, and it's great being able to rent a sailboat or Jet-ski and launch right from the beach. I saw a few dolphins one morning. At night, you can play mini-golf. Highly recommended.
The room had a free safe and a mini-refrigerator, and the grocery store is about a mile away. The kids can buy a hot dog and fries for only $4 at the pool. So you need not spend a lot on incidentals if you don't want to.
It's not quite the Hilton Waikoloa Village, but it's a great place to take the kids. Just remember to use sunscreen!