Atkinson is an English-language surname. The name is derived from a patronymic form of the Middle English Atkin.
These are much more conservative than state laws, in general (for instance, everyone should be in a booster seat from about age 4 to at least age 8) but remain less conservative than some of the european standards (for instance, the European Child Safety Alliance recommends that children remain in rear-facing carseats until 3 years of age).
As a guide children under the age of 12 should sit in the back seat on the correct child seat for their age, so for your son of 7 that would be a booster seat. Contrary to popular belief the safest place for a child to sit is the middle seat of the back seat of the car, as long as it has a 3 point seat belt.