That navigator was probably from before the soda was added to the deck 9 station. There was a program for $5 per day for unlimited soda.
The way it works now, the only time you're charged for soda is if you get it from a bar. It's my understanding that there are soda stations in the Deck 9 buffet area, and restaurants have always had free soda. Just be sure your kids know that if they go to the bar next to the Goofy pool, they're going to be charged for soda.