The accident occurred at about 9:43 PM immediately following the fireworks display at Parson’s Point on the lake south of the Wahweap Marina, according to the National Park Service.
The three victims were seated on the bow of a 23-foot watercraft when it struck a rock outcropping island ejecting them on to shore, according to the Coconino County Sheriff's Office. They were ejected onto the shore.
Seven other people on the boat were not injured.
National Park Service and Arizona Game and Fish officers rendered first aid to the children and woman.
The boy was flown to the Flagstaff Medical Center by Classic Medical Transport where he was treated for non life-threatening head injuries. The woman and girl were transported by the Page Fire Department ambulance to the Page hospital where they were treated for non life-threatening head injuries and soft tissue damage consistent with blunt force trauma.
Coconino County Sheriff's investigators do not believe the watercraft operator was impaired and they do not anticipate any enforcement action. The investigation is ongoing.