There is a reason why theme parks like Disney ban anything pulled behind, such as wagons and coolers.
Even rollaboard suitcases can be a trip hazard in crowded terminals. Trunkis I believe should be banned as I see at least once a month accidents where either adults or children are injured.
As mentioned above, people don't expect certain things to appear suddenly outside their normal line of sight, and this is unusual enough that most people wouldn't be on the lookout for it.
As for diaper changing, there are many threads here on how to change a child too large for the change table in the lav. Generally most people use the change while standing method, or the closed lid of the toilet, depending on the age and ability of the child. This may help
http://www.flyertalk.com/the-gate/bl...-toddlers.html
Whatever method you choose, please do not change the diaper on the seat, in the bulkhead area, on a tray table, or really anywhere outside the lav.