If the girls running the day camp would make preparations before Tisha B’Av, then perhaps they would be able to receive payment using something called havloh, like we find in Orach Chaim 306:4 regarding sechar Shabbos [being paid for jobs carried out on Shabbos]. Although one isn’t allowed to receive money for work done on Shabbos, if one does a job which took three days to complete, for example, it took Friday, Shabbos and Sunday, one is allowed to receive £150 for the three days of work, which equals £50 a day. Although, one is being paid £50 for the work done on Shabbos, since it’s swallowed up with the other payments, we don’t look at it as sechar Shabbos. And we don’t find that there is no berachah on money received in such a manner. Therefore, in our case as well, if the girls would prepare beforehand, and then they get paid for their efforts on erev Tisha B’Av and Tisha B’Av itself in one go, it could be that there would be no problem of “not seeing any berachah”.
However, there is a big difference between the two cases. In the case of sechar Shabbos we are talking about someone who does a job for a week or a month, and the Mishnah Berurah (s.k. 18) explains that the reason one is allowed to pay for Shabbos, is because:שאפילו אם יחזירה פועל בתוך הזמן אינו מנכה לו שכר השבתות מזמן שעבר הואיל והוא בהבלעה עם שאר הימים – “Even if the worker would back out before end of the job, he wouldn’t lose out for the days of Shabbos that have already past, as they are included with the other days.” In our case, however, if the girls would prepare on erev Tisha B’Av and on Tisha B’Av itself they would cancel the camp, they wouldn’t receive any money, therefore, perhaps havolah doesn’t help. Tzorich iyun.
