Paid holiday working - Union is saying this is voluntary but we are insisting that this is solely at the discretion of the management

We are wanting to call workers for duty on a paid holiday. We are paying more than the statutory norms for this.
However the Union is saying this is voluntary but we are insisting that this is solely at the discretion of the management. However we will pay the statutory payments as per the Act . Legal opinion is also in favour. However would like to have opinion of persons who have already been in this situation

You can ask the employees to work on a declared holiday by informing them in advance in the prescribed form and sending a copy of the same the Labour Officer. This should be on one condition that the employee shall be paid double the rate of wages for the day and shall be given another day as compensatory holiday.
Asking the workers to work on a holiday following the above is a right of the employer. But this 8 hours working will be considered as overtime working and when the overtime exceeds the maximum permitted as per the state rules, you will be in trouble. You can also say that abstaining from overtime work is insubordination but the same can be challenged by the workers and union saying that working on a holiday is purely voluntary and no employee shall be compelled to work on a holiday. By calling them for work, the very purpose of declaring the holidays for the year in advance will be defeated.
Therefore, the issue has to be faced considering the importance of holiday, religious sentiments etc.