Yes, sudo is 100% the way to do something like this. You can grant any ability to any user that way, with or without passwords and other such things. You would allow the user you want to execute adduser or useradd, whichever you like.
If there are mapped drives from a linux server visable in windows, then you may need to make it the samba commands for adding sambausers. Don't use samba, so I can't tell you what the command would be.
Mapping the drive in windows is just a permissions issue. If the new user at least has read permissions on the directory you want them to map in windows, they can map it.