Suggestions for teaching selection sort with candy
Actually, I might suggest a slightly different tact: provide a variety of candies (small boxes of nerds, Hershey's kisses, and the like) and have them selection sort by preference order.

They can also sort by height, brightness, weight, or duration of the candy experience.

And as long as you're at it, you might first have them just sort it one of those ways however they do it naturally, which can lead to a nice discussion about why we can't articulate what we're doing very well, but it's some sort of massively parallel selection sort.

Then you can do a number of sorts, culminating in your selection sort by preference order.  And at the very end, tell them all to look around at their neighbors sorts to see if there are any obvious trades that they should be making!