I don't understand why people say "take the DLR Express ~ you won't need a seat." This is your child why would you not want them in a car safety seat when in a moving vehicle??? Buses are safe for children (all of us) because of compartmentalization but they aren't big enough for this till 5+ years old! Is your grandchild under age 2 ~ if so have they purchased a seat for him/her? If so use the car seat on the plane ~ if not gate check it, there's always a chance the flight won't be full and they could use the seat anyway, most babies are more comfortable in their car seat on flights cause they're used to it in the car, it's safer anyway. My DD's (5 years old) seat on planes is the Cosco Scenera/Scenara (she's almost too tall for it though) it's cheap, easy to install, good from 5 lbs up, easy to carry on your back through the airport or plop in a stroller ~ with the child buckled in the car seat and go through the airport like that. It's a great 2nd seat, seat for Gma & Gpa's car.
PS ~ I'm a child passenger safety tech. I'd be happy to help if you have other ?'s or you could check out the website ~
www.car-seat.org
HTH!
I'm on of those who said they wouldn't need it on the bus or airplane. While I understand and highly respect your profession, and the fact that I have 2 toddlers myself, I still disagree with a couple of your points.
For the record, I do haul 2 huge Britax Marathon's with me when I travel, as I rent cars, take cabs, or stay with folks who have them, so I'm not speaking from an unexperienced perspective. I know what a pain in the it is, but we do it to save money on the other end!
1) These are not school-style buses or city buses like at WDW - which the recommendations you quoted apply to. They are luxury tour buses. As with the other types, there are no individual seatbelts or latch to fasten the seat in.
I actually called Gray Line and spoke with them a couple minutes ago and they do not allow passengers to place their children in car seats. According to them (and this is also how I felt), it is actually more secure holding your child in your lap than in a carseat that is not attached to the seat of the vehicle. BTW, at WDW, the same rule applies - you can't use car seats on their buses either (which are the city bus style).
2) In this travel environment with airlines cutting the number of flights to established destinations, as well as entire routes, you will be VERY hard pressed to find an empty flight with a lot of open seats they will just give you for having an unpaying lap passenger. At one time that was true, but not anymore. Flights to the Los Angeles area are PACKED. There are simply too many people and not enough flights. If the airlines finds that they have a flight with too few people, they will simply cancel it and rebook folks to save money. (Southwest does do this on some of it's internal CA routes. Happens to my friend who lives in Sacramento all the time.) If you didn't pay for a seat for your child, it's a pain to get that through security on a slim hope, run it down the terminal and then gate check it, then haul it back at your destination. Just bag check it when you arrive at the airport and save yourself the time and enery, since you'll be manhandling that, the stroller, the baby, all the fluids and special things needed at security, your personal belongings, etc. The less "special items" you can take through security, the smoother things will go and the less stress you have.
My conclusion is if you are coming in and taking the bus, don't haul the extra car seat. As the OP said, they are bringing one, it just won't be at the airport. Why have 2 hanging around for no reason.