@Nikhil107
@2hr is a significant time for 6 people but also are we talking afternoon dinner time midnight? I would decide based on the Guests actual experience. 6 people in a driveway at midnight for 2 hours, I would be kissing butt because if me I would be a very irate Guest.
Dinner time so 6 people had to eat out. As a Guest that would be irritating because your broken lock meant dinner for 6 (not cheap) so I would use the standard 30% refund on the room price and depending on my market at least a decent dinner for 6 price.
If the middle of the afternoon probably frustrating. I would do the 30% refund and something for snacks for 6.
Doesn't guarantee a good review but you can write an honest response so future Guests are aware if something goes wrong and your fault you own your responsibility, which also tells future Guests the expectation is for you to behave the same way.