The miskie solution to the gate would involve a solenoid and an electric timer.
1 ) Set gate so that it swings shut by itself.
2 ) add a small steel plate to the top corner of the gate, that when fully open, will come in contact with a post. mount the solenoid and the timer on said post.
3 ) strip the solenoid, exposing the electromagnet.
4 ) trigger the solenoid with the electric timer - allow the guest to set it for how long they need the gate open.
- and if they forget, once the timer runs out, the circuit breaks, cutting power to the electromagnet, which then releases the gate, allowing it to swing shut.