For what it's worth, I've had three kids in a Prius ages 2-6 (the oldest was tall enough to use a booster in the middle) and there are narrower full car seats.

For what it's worth, I've had three kids in a Prius ages 2-6 (the oldest was tall enough to use a booster in the middle) and there are narrower full car seats. One fancy option is https://www.multimac.com/range https://www.multimac.com/range, which even includes 4-across options.