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If you have applied 485 for your children (derivative of your application), the receipt notice acts as their status. Their status is AOS - adjustment of status. You need not apply for EAD for them unless they plan on working. Apply EAD if they want to work and AP if they plan on travelling out of the country. Alternatively, you could apply for an extension on your H status which is extendable beyond 6 years in your case. However, to get a stamp you may need to go back to your home country since Canada and Mexico do not seem to be issuing these currently.