Hi,
I talked this with an engineer who support VCA8500 device. He suggests the below plot with AC coupling. AC coupling is for solving 1.5V and 1.65V VCM difference. This difference is big enough in some cases. So AC coupling is a safe play. The frequency is very low, so no need to have too fancy circuits, like ADS5296 circuits.
The datasheet of VCA8500 specifies the output impedance 1ohm, and the input impedance of ADS529x family is 1Kohm. ADS528x family is similar to this but I'll confirm this with designer of this device.(Please visit the site to view this file)
Thanks,
KW