vCenter comes with a scheduler which is well hidden in the WebClient compared to the old (Windows) vSphere Client GUI. But IIRC you only can perform actions on a single element like a VM and not on all VMs within a Folder or on a Host.
So maybe its easier to write a small Powershell script to shutdown all VMs on a given Host. This only works well if VMware Tools are up and running in the VM, otherwise more actions are needed.
To bring back the VMs online after the Reboot you can use the VM Shutdown&Start feature of the host or just use a powershell script again. It also depends if VUM will set the Host into MM or not for applying the patches... i think it will enable MM so the VM Shutdown&Start canot be used.
Regards
Joerg
