Both mommies and daddies need a backpack when travelling with their families, mainly to hold everything that is irreplaceable, like the passports, other important documents, cash and credit cards, phones, and wallets. Even if everything else is lost while travelling, this backpack (or, a purse) should not stray away. They should be kept with the person at all times, under the strictest guidance.
Young children should not be allowed to carry any cash (a small amount is fine) with them, or their own passports, no matter how reliable they are. Important documents should always be with the parents or the person in charge, and they should always be close at hand. If you are carrying life-saving drugs that you might need at any moment, they should also be inside the backpack or the purse rather than in the hand luggage.