It's probably too late to answer this question posted 8 months ago. However, perhaps someone else will have the identical question in the future--and this reply will help them. Yes, in Part Five, list ALL children. Part 5 has you list A#'s if any, and the immigration status. If a child is a Derivative Beneficiary, i.e. F2 or F4, the lines allow you to indicate their status. If a child has been born in the last year since immigrating, he or she may be a United States Citizen depending on all the facts in your case. Children who are to have the conditions removed as petition derivative beneficiaries will all be required to have the biometrics fee ($80 each at the time of this reply--always check the petition instructions and fee schedule- everything changes!). Other children would not be involved in the process, but need to be included on your I-751 petition. IF the petition wasn't timely filed, such as within 90 days "a window" two years later marking the date of the (first interview), then it should be filed ASAP. If significantly later, the matter might have to be adjudicated in immigration court as relief to removal/deportation.