May want to have a notarized letter from the parent/s of the kids, stating that you are allowed to have the kids with you and take them out of US. Silly sounding I know, but my wife just had this issue arise Friday. She and our daughter are traveling with a 17 y/o female, TSA hit them up for said letter from the parents of the 17 y/o. Good news was that same TSA agent said he was 'allowed to use his discretion' on the matter, so they traveled on. Just a CYA thought...