Travelling abroad

[Morlaf]

Hello. WIdowed father of two girls living in the UK. I am taking the girls abroad for the first time this summer. I have a different surname to my children. What do i need to have with me (other than passports) in case ppl think I am kidnaping children?

Birth certificates showing you're their father maybe

I'm a widow too. I take passports, birth certificates and their father's death certificate. So far, we've been abroad several times to various countries and no one has asked.