First of all, prepare yourself for a really wild time! I think Kidani has great animal viewing from your room balcony (if you have a savannah view) or from the main viewing area near the lobby. There are wonderful rocking chairs outside the lobby where you can sit and watch the critters. There's also a cool "story rock" where the storytelling takes place at night that you can walk out to that's in the midst of the savannah. When we were there the giraffes were the closest we'd ever seen! If you get a chance to do the storytelling, it's really cool.
The pool is a bit tricky to find, but your 4 year old is probably going to really love the water playground. It's a much smaller pool area than at the main Animal Kindgom Lodge building (Jambo House) but also less crowded. You might want to plan time to walk over and enjoy that pool, too. It's about a ten minute walk between buildings.
We liked being able to park the car under the Kidani building (in the shade and out of the heat). I also think the parking location helped offset the walk down what can be endlessly long guest room hallways (especially when you are coming back from theme parks, carrying a sleeping child).
Note there's no counter service restaurant at Kidani, though you can get some lunch-type snacks at the pool bar. We always do breakfast in the room (bagels and such we buy from Publix in advance) because it's a haul to the Mara at the main building, and we are usually jetting out to parks and don't want to take the time for a longer breakfast.
We haven't used the game rooms or kids' clubhouse ourselves, but we always peek in when we go by, and it looks like the kids in them are having a blast.
If you can get your teens to babysit your youngest a while, it might be nice for mom and dad to go enjoy a beer or glass of wine at the Victoria Falls bar in the main building. The aromas coming up from Boma are equally as intoxicating as anything you can drink, and it's dark and romantic.
Hope you have a great time!