It really depends on how appropriate u want the humour to be maybe add little aspectsd of modern day life for instance the three kings could bring a iphone,ghd's and a gold chain little things like that.
Depends on the humour how u want it to be dry,witty you get me?
But you could have maybe like an aspect of other characters to like make it funny like a random chicken or someone in the news come on stage and go "Oh wrong play sorry"
Etc
Hope this helps if u want any more ideas contact me x