Almost more than 10 people remained absent or took leave for the month of August 14. Firstly, it is not clear whether they applied for leave or not. Secondly, if the employees applied for leave, has the head of the institution, in this case, the appropriate authority, sanctioned the leave with prefix and suffix holidays? Thirdly, in cases where the leave has not been sanctioned and the employees joined at a later date, what was the reason for taking leave at their own interest without the appropriate authorities' approval?
In case you would like to sanction leave without pay, the reason may contradict the genuine leave taken by the employee, and the employer may not be interested in considering the leave taken as appropriate. Furthermore, this is a case of regularization with valid reasons. Also, please establish whether all the employees are relatives and have taken leave for a particular or specific reason, such as a family function or village event. This requires consideration within the leave rules, and only then can the question of action be addressed.
However, from your words, it seems the authorities are genuinely interested in regularizing the leave with salary, as you have only inquired about festival/government holidays. Thus, without any suffix or prefix in between, you should regularize accordingly.