All hotels have great pools for kids, but I think the water cannons at RPR are the most popular with the small set.
Yes, all the resorts have character meals, usually on weekends. You don't have to be staying at a hotel to attend its character meals. And all hotels are within easy commuting distance of one another thanks to the boats.
If you're going to be there for several nights, you don't have to choose between the parks. Do both with a multi-day pass. Both parks have shrewdly included attraction-packed area for younger children, KidZone at USF and Seuss landing at IOA. Other kid-friendly attractions are sprinkled around both parks.