There is a difference between something being a secret and something being private.
Get it?
If they know, so what.
It does not mean they are now privvy to all financial discussions and descions in your household.
I know how much the Powerball person one, saw the newsconference, but that doesn't mean I get to be in on his/her financial dealings.

Your DH is right. There's nothing to worry about. It's none of their business and they probably didn't even notice.