I had a situation when traveling by air. They could not deliver the car sit when plane landed and they told me that they will deliver the car sit in my address but I can take both kids (under 3 at the time) on adults lap. I also talked to a texi driver and he told me he has seen so many of his passengers had put their kids on lap.

Its in virginia and ask someone from your state. Its better not to travel that many people together for safety reason.

Good Luck.