We booked 3 nights for $99/night, including the waterpark fees. Altogether, after taxes and whatever else there were charges for, the total was under $400. The price on the screen was the full price, no other hidden fees. The waterpark is available from the moment you arrive (even if your room is not ready) and you can use it the full day after you check-out (there are lockers to use to shower and/or change).
The website is absolutely maddening. I tried calling the 1-800 number for more information but that was completely useless. You're calling a hub center, not the Orlando location. The woman I spoke with was unable to answer any of my questions. It was frustrating, but I decided to go ahead and book on-line and take my chances. There were specials for book 3 nights and get the 4th night for 50% off but I didn't take advantage of that.
I just checked the website and there seem to be even better deals for July. Florida Residents can book a night for $83.85 including full use of the waterpark. They are also still running the Book 3 Nights, Get the 4th Night 50% off...
We checked in at about 10am and within 15 minutes we were in a room directly over-looking the waterpark. I wasn't expecting to get a room that fast or in such a great location so it was either good luck or the place was empty... After exploring the resort, we found another large standard swimming pool and hot tub that seemed very nice and exceptionally quiet. There was never anyone in it, but it looked very relaxing. There were families staying in that general area that had a short walk to the waterpark area. I have no idea how rooms are handed out since it seemed there were plenty of empty rooms around the waterpark.
How old are your DD and niece? There were some families with older kids/teens that seemed a bit disappointed. There are 3 nice sized slides for taller kids and adults, but other than that the large play structure with slides and covered kiddie areas were a huge hit for the younger kids - not so much for teens.
I have no problems answering questions. I'll help if I can!