DLO is one option, though I was under the impression that it's of more use for a sort of continuous backup, rather than routine backups. I've never looked in to it that much.
If overnight backups are what you want, then you can use remote agents on XP workstations without any additional licensing requirements (I think).
Wake On Lan isn't implemented in BE, but if you are using static IP addresses, then if you can find a script to wake the workstations, you could set this up as a pre-command to be fired off before the backup starts.