I don't have any pics or movies I can share but I can say this. The YC/BC is our favorite resort(s). I think of them as one. Anyway, we don't have kids but I think a 4 year old would LOVE Stormalong Bay. I see kids screaming and crying when their parents are trying to make them leave. They have a kiddie pool section - a great slide - a "whirling pool" section, and even a small "lazy river" section. There's often a volleyball game going on. It's like a mini water park. I can't imagine a child not going crazy over it. Heck, I'm 41 and I go crazy over it.
Other than Stormalong Bay, we love walking to Epcot and boating over to MGM. The boardwalk area is tons of fun. I'm sure you and your child will have a great time.
PamNC