The worst alternative is to put the shoulder strap under one arm. As a driver, check to make sure that everyone in the car is buckled in before you drive, even if only driving a short distance. Most accidents do occur on surface streets within five miles of home. Children have been seriously injured by being propelled against a loose-fitting belt. Your question highlights a poignant situation.
Automobile accidents are responsible for more deaths in middle childhood than any other cause.
There are an additional 100 children injured in car crashes for every child who dies. Air bags are a case in point. It is particularly disturbing that some of these deaths have occurred in low-speed collisions. Children should ride in the rear seat, particularly in cars with airbags. If they do ride in the front, the seat should be adjusted to be as far away from the dash as possible.