When we stayed at Kidani, we timed the walk from our door to the Mara. It was ten minutes at a liesure pace. It was not far, or difficult. All sidewalks. Our room was on the wing closest to Jambo though.
The Park Buses go to Jambo first, then Kadani. The Downtown Bus goes to Kidani first, then Jambo. I never found seating to be a problem, or transportation times to be excessive. You can use the buses to go from one area to the other, but we found walking it to be quicker.
Someone correct me if I am wrong but I think you can use Kidani's pool if you are staying at Jambo. (We are DVC members so I know we can) That being the case, I would recommend staying in Jambo, and going over to visit the pool at Kidani, as it is much, much better than Jambo's on the Kid Fun scale. (I'll give Jambo a nod on size) Especially if you think you will be eating any amount of counter service at your resort.