Have you seen the vPC Best Practices Design Guide?
http://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf#page=1&zoom=auto,0,672
It states, "orphan port suspend is available only on physical ports, not on port channels. To configure orphan ports suspend for the port channel, apply the configuration for all member ports of the port channel."