A 30-year-old woman and her 7-year-old son were killed and her two younger children critically injured yesterday morning when their car crashed into a van on a busy Long Island thoroughfare.

Keri Trinca, 30, of Manorville, and the kids were off to meet her husband for a fun day of family go-carting when her 1998 Honda Accord collided with a 2002 Ford E350 just before 8:30 a.m., police said.

Mother and son were pronounced dead at Peconic Bay Medical Center in Riverhead. The other kids, a 4-year-old girl and a 2-year-old boy, were fighting for their lives.

Van driver Steven Vonfricken, 51, and his only passenger suffered nonlife-threatening injuries. Police said the accident was under investigatiion.