Sensing human presense (finger on trigger) could become a bit challenging.
Ways to detect (and unlock the motor):
Capacitive touch: Esp32's capacitice touch pin attached to the internal metal construction to sense fluctuations in capacitance, as soon as human skin touches it. Would need some kind of conductive touch interface, like a metal-trigger.
field sensor: some kind to hall-sensor that detects fluctuations in its field without direct contact and with a bigger radius, e.g. iqs231.
accelerometer: detection of motion to determine, whether the toy is held or layed down on e.g. a shelf. Drawback is false positive, while transporting the toy.
Sensing human presense (finger on trigger) could become a bit challenging. Ways to detect (and unlock the motor):