You might want to do some research to see what appeals to you. Yes, you can see a lot of each park in one day for each, but if you have the time, you'll have a better trip if you allow more time than that. We've been on two long trips in the past year, and still have missed some stuff in the main 4 parks, and we haven't gone to a water park at all. You can see the highlights for your group in a day, but not all the shows and rides. And there are always things you want to do more than once. And if you do character visits and table service meals, it would be hard to "do" any park in a day.
No matter how well you plan, be aware that you can't do it all. WDW is HUGE!