Welcome, Melissa!
You are in for such a treat when you head Under the Sea to swim with Nemo & Friends at
Disney's Art of Animation Resort.
You are absolutely correct that there are three different "themes" to the
family suites: Finding Nemo, Cars, and The Lion King. Generally, you will see that the Finding Nemo Suites are a little more expensive, purely because their location is the most central. Each of the buildings that house a Finding Nemo Suite borders the pool and is located between the Disney Skyliner and the main building with the food court.
Now, The Lion King and Cars family suites have the exact same layout as the Finding Nemo suites, but they are located to the left and right of the main building. Each of these locations also has a nearby pool, but you are welcome to travel across the savannah or down the open road to
swim with your favorite pals from the reef.
Mellissa, occasionally you will see that you have the ability to book just a "Family Suite." This does not mean that the room is not themed, but that they will assign you a themed room upon check-in. If a specific theme isn't super important to you, this booking option often can be a great value!
I hope that this helped answer your question, Melissa. Please come back here to planDisney if we can help answer any other questions to make your vacation magical.
See you real soon!
Sarah B.