During the family Christmas, I'm going to tell my grand kids to be excited for their present from me, since I put a lump of coal in shoe boxes and wrapped it for their presents.
Wow that seems pretty cruel.
I'm not trying to offend them. I just wanted to do something funny.
Lying to children is hurtful since they don't understand. They will feel betrayed and hurt and might not want to forgive you.
So, I shouldn't make jokes with them?
If they are really young it is very inappropriate. Maybe if they are teenagers they can handle the emotions better but it is still a cruel joke because only "bad" kids get coal.