Infants should be in a rear facing, properly installed infant seat until they are at least 1 year old and weigh 20 lbs.  At that point they can be in a forward facing seat with a 5 point harness until the age of approximately 4 and weight of 40 lbs.  Children age 4-8 years old should be in a proper booster seat using the seatbelt.  This information was found at www.nhtsa.gov.  We treat many people with injuries derived from car accidents.  The last thing we want to see is an injured child who was not properly restrained for their own safety.  Car accident injuries (even the hidden ones) can occur at speeds as low as 5 mph!  There is no such thing as "It's just up the street, we're not going that far etc."  Know your restaint/seatbelt information and use it... It will save you life and possibly the lives of your children.