Hi Keena,
Any requests should be noted on your hotel reservation. If you booked directly through Walt Disney World, call 407-W-DISNEY or
(407) 934-7639 and ask to have your request noted on your reservation. If a travel agent booked for you, simply ask your agent to put in the request.
Requests are not guaranteed. The more general your request, the easier it will be for the Room Assigner to accommodate your family. However, if your goal is to be near a certain part of the resort, it's best to ask "near the food court" or "close to the Dig Site pool" rather than asking for a specific building.
If you want to be anywhere in the Casitas section of
Coronado Springs, just ask to have it noted on your reservation. Due to the resort's sprawling size, there is no one section that is close to everything. For example, the Casitas are close to El Centro (the main building with food court, etc.), yet they are a long walk to the pool area at the Dig site.
Casitas 1, 2, and 3 are preferred room locations and are only available at an additional cost.
Coronado is a beautiful resort. I've stayed there a few times and have enjoyed all of my stays. Let us know if you have any additional questions!