Probably the easiest way to do this is do the following:
1. Create the user and assign their home directory.
2. Create the symlinks to appropiate locations you specified above.
3. If you don't want them to see other directories or browse, chroot them or jail them to their home directory.
4. Setup and change the permissions accordingly on the two directories they will have links to from their home directory.
5. For added security, give your users a false shell, so they can basically only ftp to the server to update their web pages, you can do this by changing their shell to something like /bin/false and add that to your /etc/shells file.
Hope this helps you out.