Jerry Peck
This sounds like your water heaters are set up for maximum gallonage capacity for hot water storage, with the recirculation pump to keep hot water only just a few moments away from every hot water point of use.
With this being the case, I would recommend piping the recirculating system to the second water heater in the series to provide the maximum stored gallonage of consistent hot water. This should also be more efficient for fuel use. The first storage tank will not come on as a result of heat loss due to the recirculating system piping, however, it is always available to provide back up hot water for peak use periods.
