This is completely my own personal opinion. I would never rent car seats or use car seats that I don't know the history of. I don't trust the rental companies to take care of things the way they are supposed to, nor to actually throw away and replace a seat if the vehicle has been in an accident of any kind.
I would either bring your own from home, send any you need with your parents, or just buy them at
Walmart when you need them. That would probably be cheaper than renting one anyway.