I'm going to let you in on a little trade secret: There is script astronomers are supposed to follow today when explaining what the solstice is, and that script goes something like this:
2) Ask the strawman "Ah! But if that *were* the cause of winter, then why is it summer in the southern hemisphere right now?"
4) Bonus Points: Use the words "obliquity", "eccentricity" and "precession" as much as possible to give your audience some impressive words to drop at their holiday parties.
Credit: @apod 2009 July 3