They do show the welcome video, but it may be hard to see for little ones since the monitors are above head every 4 rows or so.
I would personally be more concerned with wait times in the lines at parks versus a short bus ride. Start teaching your twins what to expect and try to help them understand what is going to happen once they arrive. The airplane flight is also going to be much longer and the more prepared you are and the twins are the better.
Have a great trip.
duds