1000$premium不cover孩子的？

I-907 premimum service only applies to H-1B beneficiaries, not extending to H-4 dependents. Since the employer usually submits the H-1B petition (I129) along with I-539 for H-4 dependents, USCIS often processes them together. However, it is only a courtesy.
You have to apply for an H-1B visa with your H-4 children anyway. H-4 approval notice alone is not sufficient for H-4 visa application. You still need to submit all H-1B petition materials and evidence to prove relationship between you and your children.