Florida law, according to our Tiffany driver, states that your child does NOT have to be in a car seat or booster on public transportation. Tiffany is considered public transportation.
Three out of the 4 times we requested a car seat the driver brought one. They weren't exactly what I would call stellar seats but did the trick. One time the driver didn't have one but fortunately I had brought one so pulled it out and used it. He said he knew I was traveling with one and didn't have one available. Uh-huh!!!
Anyways, I'm told by Tiffany that they will provide you with a car seat if you request it. I always call the day before and remind them.
But, according to the law, they don't have to be in one. That must be how Disney gets away with no seat belts and car seats on their buses. Hope that helps.