I.W. and defensive interception

[jsavorn]

Recently I had a play where the offense threw an int. and the covering official blew his wistle after a series of two fouls by the offensive team (both personal fouls).
How would I administer the penalties?
I gave the ball back to the offense and then penalized them 30 yards for the personal fouls. Is that correct?

BTW I think the rule that giving the ball back to the offense when there is an interception AND an I.W. (post interception) really isn't fair.