This. My ER handles a lot of critical patients being a trauma center. We almost always incorporate the family in critical patients, letting them stand with the chaplain and watch us work on their loved one does a lot of good in the long run. But, this is in a large trauma bay with adequate staff to monitor the family.
In an ideal world, you would have the room to have someone sit with the kiddo in the ambulance and explain things to them, but we don't live in ideal worlds and truth is sometimes in EMS it isn't possible to bring family members along. If possible and dad was critical, I would have PD bring them following right behind so they can be at the hospital where they have resources to handle these things.