Most states have strict and specific laws regarding children and car seats. Due to their size, children can be seriously injured in a car accident. While it’s understandable you don’t want to spend extra money, you could face fines and driving record points by not properly restraining your child. In some cases, this may be more expensive than purchasing a safety seat.
Since you’re visiting family, try to see if you can borrow a spare car or booster seat. There may also be a local business that rents car seats. Even if you do have to spend the money to purchase a car seat, it’ll be worth your peace of mind and child’s safety.