Reading it through again, I think there were two events. The children’s party in the evening. And another meal, with booze, served to adults - probably at lunchtime. Most of the besieged were soldiers and, at that period, the main meal of the day was served then (although generally known as “dinner”). The extra “evidence” is that there was one potato “for each man”.
With supplies heavily rationed during the siege, the issue of booze can’t be per person and it suggests that this must have been a small group - maybe a platoon (or each small group was given a booze ration)