What is the minimum age/requirement in Texas that a child can ride without a car seat?

Don't get a booster, a 2 year old is way too young and likely too small. The Cosco Scenera runs around 40 bucks at WalMart and should work in your situation. It rear-faces to 35 pound and will work forward up to 40 pounds. Let dad hold onto the seat for furture emergencies or situations like this.

Minimum age, there is none, if you have a baby in your car it must have a car seat according to the law. 2 is not old enough for a booster, the next one up. I hear what you are saying though and don't know how to solve that problem.

They say until the child is 4'9'', it needs at least a booster seat. I live in Texas, and that's what I know to be true. But a two year old definitely has to be in a car seat. It would normally be the parents' responsibility to get one for their child, car or not, but in this case that hasn't happened obviously. I would ask the dad if he knows anyone he can borrow a car seat from, someone who has an extra or someone who won't be needing it during the time he will. If this won't happen, consider asking him to buy one. If you're not comfortable with that and you still want to give him a ride, go get one yourself. The final responsibility lies on you, since it's your car and you're driving. Is it just for a day? Does the dad get rides from other people with his son? Consider asking the dad if he'd like to keep the carseat you buy, for future use. Consider splitting the cost with him. That is, if you're concerned about the safety of the child when he's not with you. If not, consider buy a carseat just for that day, and then returning it later. I know that most people would say that's horrible, but sometimes you gotta do what you gotta do. And if it comes between doing that, or letting the kid go without a carseat, I'd do it in a heartbeat. Also, the age doesn't really determine whether or not a kid can use a booster seat. Go to Wal-mart or something, look at booster seats. They will have a minimun weight and/or height. If this kid is a bigger two year old, he may be able to use one. And if so, that's great, as booster seats are A LOT cheaper than toddler seats. Try this option first.