What application form are you referring to and what is nationality of the person travelling with them?
Are you still interested in receiving a live phone call?
Ok. Anyone travelling with your children must have leave to enter the UK. If the person you are proposing to travel with your children is Nigerian, she will need to have a visa. Also you may need to speak to the airline regarding their policy in this situation. I am certain consent from both parents will also be required. I expect there to be a strict policy regarding children travelling without their parents or family members especially if they are very young.
The person travelling will need a separate visa to travel.
Can you please rate. Thank you