Bringing Minors?

You should have a photocopy of the parents identification(s) and your Identification.
Written on that paper, a letter from the legal parent(s) or guardian(s) stating that they (by names) give you (by name) guardianship over minor(s) (by name) during the dates (dates from & to) in case of emergency.
Then they need to sign and date it and you need to sign it and date it.
At that point you have responsibility of and for the minor(s) and can sign for them at gate like normal. At which time, you will be responsible for their actions and well being.