May one slap five with his parent?
One may do so with consent of his parent out of jest and playfulness. If however, any damage or pain will be inflicted to the parent then it is forbidden to do so, even with his consent. This applies towards any person and not just a parent.
 This follows the same law as slapping five with any other person, as there is no wound being created in the process and the Rama ibid states that hitting a parent without release of blood retains the same prohibition as applies towards any person. Now, since slapping five with another person involves his consent it is therefore not considered hitting at all, the same way that taking someone’s money with consent is not considered stealing at all. It is the consent that makes a difference between whether the act is stealing or charity, and whether the act is hitting or playfulness. Now, although it is forbidden to hit another Jew even with his consent, or to cause him pain [Admur Nizkei Haguf 4; Rivash 484] nonetheless slapping five does not cause one pain at all, or any damage, and is hence not considered within the category of a hit. Hitting is defined as doing an act which is either painful or damaging to another person. If, however it is neither painful nor damaging then it is not considered a hit at all.
 Admur Nizkei Haguf 4; Rivash 484