Joint or Collision without rigidbody

Hello.

I've got main object "Car". Inside we can find children "Active" and "Other". I have to use Box Collider to Active object beacuse I have to use OnCollisionEnter in script, but how we know Box Collider doesn't work without rigidbody, so I added it to "Active". Now OnCollisionEnter working fine, but when I'm moving "Car" object I want to move the same direction every child. When I use "is Kinematic" in Active's rigidbody it doesn't move anywhere. When I freeze all position the same. When i turn off graviti it just don't drag down.

How to change position of children relative to parent without "foreach transform position" - it's really primitiv method.

Any help? Marshall.