To configure CMFNotification, you have to go to the ZMI. Then click on the portal_notification object and fill the Rules on workflow transition (users) rule with something like:

python: transition == 'submit' :: python: context.getGroupMembers('Reviewers')

Fill the Rules on workflow transition (mail template) with something like:

* :: string:workflow_mail_notification

Save the configuration and add the following script somewhere (e.g. in portal_skins/custom) group_id parameter:

from Products.CMFCore.utils import getToolByName

tool = getToolByName(context, 'portal_groups')
group = tool.getGroupById(group_id)
if group is None:
    return ()
return group.getGroupMembers()

Add a group_id paramater to the script, and a Manager proxy role. (Warning: it lets any user able to list users of a group on your portal. It is up to you to consider whether this is a security risk.)

You might want to include this script in a product rather than putting it in portal_skins/custom.