If you are not paying W-2 wages, then you will have to pay 6,497 (1/(1-0.0765))*6000 to account for half the social security being deducted. They would also have to pay self employment taxes ~14%. Are they really going to working 86.6 hours each for you? How many clothes do they have to model? I'm not personally questioning it, just giving you an idea of what you might have to document and back up against the IRS.
The good news for you is you get to deduct the $6,497 per child on your schedule C. However if you're a schedule C, then I would be wary about creating a loss on your taxes to do this for your children. So define small business. Are you netting enough per year so that this wouldn't create a loss?