Speaking strictly from point of view of Gaia interface:

The link speed increment is not defined by the user. So if you'll perform port aggregation in VMware, the Gaia may still default to a single interface speed.
It stands to reason that you may want to present both interfaces as separate entities and perform aggregation in the bond on Gaia.
I am uncertain how the LACP will act with ESXi's virtual switch though. It is possible that you may have to tinker with the promiscuous mode settings on the port group assigned to carry this traffic.
Timothy Hall could probably chime in on this subject.