Speaking strictly as a dad, JP, I think you did fine. I'd parrot the comments that if it makes them feel better, let them keep their stash and make sure they've got some healthy stuff in there. It had to be traumatizing for them, you're not going to correct 8.5 years of f'ing up overnight. As they grow accustomed to the stability and food on the table at every mealtime, it will become the norm rather than what they were previously used to.
It's heartbreaking that it's their instinct.
Just keep being the positive influence that you are.