Hi Robin!
Thank you for visiting the Moms Panel!
I recommend this: write a letter and post it in the mail to your Walt Disney World Resort, for it to arrive approximately 3-4 days before your arrival date. Guest rooms are generally not assigned before then, so it's not recommended you contact the resort hotel too far in advance. Give an outline of where you would like your room to be located (and briefly outline your mother-in-law's requirements). On check-in, if you are not happy with your room, you can ask for another - but please remember that nothing can be guaranteed, and they can only assign you a room within the limitation of what is available for your length of stay. I would add, from personal experience, the front desk Cast Members have always done everything they can to ensure we are happy with our accommodation.
The address you will need is:
Disney's Coronado Springs Resort
1000 W. Buena Vista Drive,
Lake Buena Vista, FL 32830, USA
(telephone: 407-939-1000)
If you have any other questions, please come back and ask me - I would be happy to help you plan your magical vacation!