Lola - I just covered it with foil and put it on the front seat - that worked pretty well. I don't have a cake holder - I should probably get one, though. I just touched it up with the leftover icing when I got to the destination.
Sundae - once it was cut, it seems like it went flying. Half gone in no time! I might be making another with just a glaze to use up the buttermilk, but I haven't decided yet. I don't ever use buttermilk.
An update - though, all items were a hit.
Although, it seems like me providing all those veggie types was pointless. People mostly only ate carrots and celery.