Activate Guest Account

I don't know the terminal commands offhand, but it can be done via MCX if you're running an Open Directory server.

If I come across the terminal commands, I'll post back.

If you have an OD server, the MCX policy that controls guest access is applied to either computers or computer groups. Once the policy is in place, network connectivity has no effect until you want the policy updated/removed.

Do you have your Macs bound to OD?

Yes.

In Workgroup Manager, the steps would be:
Select an existing computer group (or create a new one).
Add the appropriate computer objects (if they aren't already there)
Click 'Preferences'
Click 'Login', then click the 'Options' tab.
Click the 'Always' radio button.
Click the box to 'Enable Guest account'.
Click 'Apply Now'

No problem. Good luck.

You should not have to add the computers, as they should be in OD after they were bound.
If you click the computer icon in WGM, you should see a list of all your machines.
If you click on the computer group icon, you can add a computer group.
Select the group you want to manage, then click the 'members' tab, then the '+' button.
You can multi-select all the machines to add, then click apply.

Glad to hear its working for you.
If you don't mind, please mark the appropriate posts as either helpful or answered for others' benefit.