13.......good relationship with both of you....
i agree that waiting would be wise.
your son will have questions and it couldn't be construed as "talking behind the others back" if all of you are in the same room.
i sincerely hope and pray that both your husband and yourself can remain calm during your discussion with your son.
rest assured he will ask each of you for your "side" later on but for now the appearance of unity with the decision seems to be the best route.