Attendance at the banquet wasn't really necessary for all the workers. It was more or less just a joint vacation for all of them. Yet Lex did not expect many to miss out on it, and indeed there was 100% attendance even just a few minutes after the day began.
The 'banquet' itself would only begin in the evening, but everyone had 24 hours of free time to enjoy themselves. In fact, there were temporary workers found even within the village, so that the workers could for once experience all the services that they were usually offering.
The experience was extremely novel, as they had never just 'hung out' with their friends in such a manner before.