To be very frank, I would say that this is one of the Labour Acts which remains unenforced. Many establishments, even in the manufacturing sector and those with trade unions, are yet to get their own Standing Orders certified! even PSUs are there without certified Standing Orders.
Therefore, practically, no establishment would go for certification due to two main reasons. Once, if you draft a standing orders, the certifying Officer would require a trade union representative to certify it first as accepted as the service conditions. In the absence of a trade union, he would select a few employees as signatories to standing orders. In many cases, these signatories will then acquire a feeling that they are leaders of the other employees since they are also signatories to the most important document defining the employee employer relationship. This could be avoided if standing order is kept in freezers until the labour enforcing authorities require that standing order should be made and certified. Therefore, I also advise that so long as your number of workmen become 100 you may follow the status quo. Alternatively, you can prepare an Employee Handbook including all the relevant matters for which provisions is required to be made in the standing orders and communicate the employees. This can also be made part of the employee joining document and you can take acknowledgement from the employees as having read, understood and accept the content as applicable to them. This would then become part of employment contract.