Sayer reportedly lives in Copperopolis and Celia and the toddler were visiting the US.
Sayer was driving a 2012 Dodge and had stopped west of the James E. Roberts Memorial Bridge at the Don Pedro Lake Vista point with his two passengers.
He re-entered Highway 120 to head eastbound, but in the westbound lane.
At the same time, a 59-year-old man was travelling westbound on the bridge.
As Sayer approached the bridge, he saw the other vehicle.
Both drivers attempted to avoid a crash, but crashed head on, causing the 59-year-old to be pinned in the front seat of his vehicle.
Fire personnel freed him.
Sayer and Celia sustained major injuries and were taken to separate medical centres in Modesto.
Ethan received minor injuries and was taken to UC Davis Medical Center in Sacramento.
Alcohol is not suspected to be a factor in the collision.
A press release said Sayer was used to driving on the opposite side of the road.
