Incorporating mobility and security into a web application

Your team is modifying an ASP.NET MVC application for an automotive dealership. The company issued Windows phones to sales staff. Office staff members access the application via their desktop computers to perform data entry, generate reports, and handle other administrative functions. The mobile devices will be used to search inventory and to check cars in and out for test drives. The application must also be viewable in a native user experience relative to the devices.

How can you ensure that both types of users have a positive user experience?
Would adding two more types of mobile clients, such as Android tablets and iPads, to the list of supported devices change your approach? Why or why not?