Since their salary is more than $15,000, they are exempted employees as they were never PF members before. If they want to contribute, you have to give consent as you will have to pay admin and EDLI charges. Via media, if needed, is if you, they, and you contribute and deposit the amount in a bank account/FD or similar and distribute interest accrued. You may give them an annual statement of the account to convey that their money is safe. PF without authorities!