I was searching on this forum about this information and didn t find anything so I want to shortly tell you about my experience about this type of case because even my lawyer didn t had any type of information about this situation.
I am talking about IR2 Visa Category (U.S citizen filling for child under 21) as you know sometimes Visa process mostly gets stuck at NVC or even USCIS and this info probably will be helpful for this category to expedite their case.
If your children are 17 years old and they are about to turn 18 , they can t use U.S citizenship act of 2000 benefits When they enter united states ,This means that they lose chance to derive citizenship from you when they enter united states.(they will get green card and will naturalize after 5 years) but you can help to change this situation for your good + win some time on NVC stage with expedite. If your child will turn 18 years old in 3 month (120 days) you can fill expedite request in NVC and you will get accepted. This means your case will be Immediately sent to U.S embassy without NVC reviews ( you will win about 3-4 month of NVC stage) and you will get your interview date really soon. But you should have paperwork (documents ready)for the interview . After your interview your child(en) can enter united states and they will get green card and derive citizenship without waiting 5 years...
p.s I m not sure if you can expedite your case from uscis stage but I m definitely sure that you can expedite your case from NVC stage.
You should be biological parent and must be U.S citizen by birth or Naturalization
Information about child citizenship act of 2000
I hope this information will help some kind of categories, good luck and if you have any questions I will be happy to answer.