Two years ago we took a friend of our sons with us to florida. They were both 16 at the time.
The FEMALE immigration officer wanted a letter confirming Chris was allowed to come with us.
I thought uh oh what on earth do we do now, I said, err we do not have one, I then looked a bit blank & felt at this point the less said the better.
Her comment "so typical of the British just send their children off".
I nearly exploded but knew I could not, I was so so so very angry as was my husband, he was waiting with baited breath for my reaction & no doubt praying I would let it pass.

With hindsight it would have been sensible to have a letter, (wise after the event) but I will never forget her attitude or forgive her unjust comment.
My advice take a letter with you & anything else you can think of in the unlikely event you get an immigration person from the same mould.

Lynne