If you need to get somewhere with an iMac, I think shipping it is probably more likely to get it there intact than checking it as baggage.
One thing I’ve seen vendors at trade shows do is to buy an inexpensive flat panel TV or monitor and have it delivered to the venue. They hook it up to a laptop or small desktop (a mini would work great for this). During the show, they collect business cards and draw a winner who gets the display at the end of the show. The vendor doesn’t have to deal with getting the display to or from the show and they get a bunch of sales leads. The cost of a cheap display these days is peanuts compared to the other expenses involved in attending a trade show.