No, you do not have to create a user account for every person who will be using the system.

The District Admin will only need to create user accounts for those individuals who will be given a specific role within the request process.
See District User Roles for any questions regarding the roles.

All other users will be able to create their own accounts and enter all of their group information.

See Create User account and Group profile for more information on how to create a new account.