Yes, so I finally got this to work by adding
scsiX:Y.sharing = "multi-writer"
to the *.vmx files of the 2 virtual machines. After that I was able to add all the vmdk's to both vm's without any issues. Is that what you were referring to by "configured SCSI bus sharing for the VMs"? I would have to do this for all future vmdk's up front because if I don't update the vmx file now I will need a reboot every time I want to add a new shared vmdk. Is there anything else that needs to be done that I might be missing from a best practice perspective.
Thanks,
-Simran