The Snohomish County Sheriff's Office, fire and medic crews responded to the accident at Sultan Basin Road, half a mile north of Kellogg Lake Road.
The vehicle rolled over and hit a tree, said Merlin Halverson, fire chief for Snohomish County Fire District 5.
The driver was pronounced dead at the scene.
Both children were transported to Harborview Medical Center in Seattle, one by helicopter and the other by aid car, the sheriff's office said.
The Snohomish County Sheriff's Office is investigating the accident.
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