Staying on the monorail if you have little children is a great idea because it makes it easy to escape the Magic Kingdom when they need a nap, and then just as easy to get back to the park for fireworks time. The Polynesian is gorgeous, and one of my favorite places to stay in Walt Disney World. However, if you also intend to save money, that resort is not the place to do it. In fact, all of the resorts near the monorail will cost you quite a lot. There is only one way to save significantly on a Disney hotel, and that's to stay off-property and drive in. Off-property hotels can cost twice what on-property hotels of the same caliber cost. The cheapest Disney hotels are the in the so-called "Value" class (the Art of Animation, Pop Century, and All-Star resorts) and none of them are near the monorail. You will have to rely on motor vehicles of some kind if you don't pay major bucks.
Our new book on Disney comes out in January, in plenty of time for you to plan your August trip. And there are plenty of money saving tricks in it!
Amazon link: http://j.mp/1c19nVd