Kidani, hands down.
1. The 1BRs have 2 bathrooms which with five people, including MIL would be priceless, I think.
2. While perhaps not a savannah view room, there are viewing areas around AKL itself where you can see animals which I'm sure your kids (and you!) would enjoy.
3. Sanaa is a wonderful restaurant, and if you dine there during the daylight hours, you can see animals from your table (currently, I believe, there is construction going on outside the windows of Sanaa, but I'd guess that will be gone by Sept).
4. The pool at Kidani is one of the better pools around, especially for kids, and it has a zero-entry access.
5. Some will say that AKL is too remote, but that's more of a state of mind than reality. Buses there generally get good reviews in terms of timeliness and frequency, thus you have access to any park with relative ease.
6. AKL has three of the better restaurants on property.
Jiko is a superb signature, so if you and your husband can get a date night, it would be a real treat.
Boma is a very good all-you-care-to-eat place and gives you the ability to choose from a large number of various foods, some with a bit of flair. And I've already mentioned
Sanaa as a nice spot for a reasonably priced meal (re: Disney standards) with great views. The first two restaurants are at Jambo, but you can walk 10 minutes to get there or take a shuttle.
7. Theming. It's second only to the Wilderness Lodge and, perhaps, Grand Floridian. As you may know, both WL and AKL were designed by the same architect, Peter Dominick, so they're sister resorts in a manner of speaking.
The other two resorts will be fine if that's what you decide. SSR has easy, as in walking, access to Disney Springs if you plan to go there a lot (if not, that negates some of the advantage of staying there). Buses are fine, but they do have a few internal stops before heading out or arriving at your particular station. OKW has the largest rooms as it was the original
DVC property, but their 1BRs (and SSRs) only have a single bathroom. So, while you may give up some square footage, for me, I'd much rather have a second bathroom--and you'll still have plenty of space for five at Kidani. Good luck with your decision!