Using analog switches with ultrasonic sensors, what to look for?
I would recommend that you use two separate op-amp gain stages and then put the switch at the outputs of these two stages. This way the switch can be used with the +5 and GND supply connections and the signal is centered in the supply range of the switch. This would typically be the optimum way to operate the analogue switch. 

There are also some advantages of simplifying the circuit path that your lowest level signals pass through to keep circuit connections short and give a better chance of eliminating noise pickup in sensitive the amplifier front end.