High five can be taught by starting with a simple hand shake and shaping the dog to raise the paw higher. Shaking hands is a classic trick, but I like to introduce “Gimme five” because it has a lot of appeal with kids, due to basketball being so fashionable. It has a great value in practical control and socialisation training.
I see lots of people who have a boisterous Golden Retriever or similar sort of “family dog” that is basically friendly but can jump up on people and knock the little kids over. I teach the boring old “sit to say hello, sit before getting a pat” etc. but it often gets untrained by other people in real life encouraging or allowing the dog to jump. Kids don’t like to be knocked over, but they’re not really interested in a dog that can sit. But once the dog learns to give a high five, the kids can invite their friends in and the whole neighbourhood will be lining up for turns. This is using the same psychology on the kids and neighbours as you are on the dog. Give them an alternative way to interact and make it fun.