As stated from this documentation http://docwiki.cisco.com/wiki/Cisco_NX-OS/IOS_SPAN_Comparison :
A single SPAN session can include mixed sources (Ethernet ports, Ethernet Port-Channels, RSPAN sources, VLANs, and the CPU control-plane interface).
128 source interfaces can be configured per session.
32 source VLANs can be configured per session.
32 destination interfaces can be configured per session.
A destination interface can be configured in switchport access or switchport trunk mode. (Trunk mode allows you to tag traffic toward a destination or to perform destination VLAN filtering.)
So I can suppose that with right filters your implementation can be done.
The only caveats/clarifications:
- is your etherchannel a trunk and some vlans go to sniffer 1 and others go to sniffer 2 ?