Using multiple HC-SR04: sharing trigger pin and interference between HC-SR04
No, you can't really share the same trigger pin, for the reasons you have already worked out. You can, though, share the same echo pin, since you know which HC-SR04 has been activated by the trigger.

To do that you will need a "wired or" circuit. The simplest method is a diode per ECHO signal and a pull-down resistor:







simulate this circuit &ndash; Schematic created using CircuitLab