My DGS, 6, is starting to appreciate jokes, but I am struggling to think of any suitable for that age group.
One I remember from when i was that age is "what's black and white, and re(a)d all over? A newspaper."
More suggestions, please 
What a difference a day makes 😢😢

) via his mum, hoping that she will read it out to him on their journey down to Devon.