To simply have a group of administrators without editing wikka.config.php you can change the line in function IsAdmin($user) in libs/Wakka.class.php from

foreach ($adminarray as $admin) {
if (trim($admin) == $user) return true;
}

foreach ($adminarray as $admin) {
if (trim($admin) == $user || $this->isGroupMember($user,trim($admin))) return true;
}

Then, you can add in wikka.config.php

'admin_users' => 'AdminGroup',

As I don't know, if there are any problems involved administrating a Wikka this way, you should have at least one admin user name entered in admin_users. A first test showed it works as intended. Don't forget to set the new AdminGroup writable only by AdminGroup or another admin from admin_users. Else, any user could write her name on the page and get admin access.

CategoryUserContributions

Wikka : UsingAdminGroups

Using Admin Groups

Prerequisites