can't add all users to _lpadmin

Hi All,

I'm trying to use Automator to create an app that simply opens terminal, and runs a command to add all users to the _lpadmin group. Here's what I've got:

on run {input, parameters}
  tell application "Terminal"
  activate
  do script with command "sudo dseditgroup -o edit -a everyone -t group _lpadmin"
  end tell
end run

This runs fine, but when I run dscl . -read /Groups/_lpadmin GroupMembership it doesnt list the new user account I created to test this.

When I run dscacheutil -q group and find the everyone group it shows no users. In fact I cant find a single group which lists all of my user accounts.

Can someone please help me with this.