I think you might be able to just list both on one Item.
Switch Power { channel="exec:command:storage_power_off:run", wol="192.168.178.255#MAC" }
The ON command to this Item should get passed to both bindings.
If that doesn’t work, create a Group, put both Items into the same Group, and send the command to the Group. The Group will forward it to all it’s members.