You handled it fine.

Big picture, though, it's a coping mechanism. Bring it up with the counselor, but if it brings them comfort I'm not convinced it's all that bad for them to have a box of food. Heck, offer to help them keep the boxes stocked with some healthy stuff.

Living in earthquake country we have boxes everywhere and lots of water, too, even in the car...since you never know.

Good luck, JP, and continued kudos on giving them a stable home environment.