I saw this photo on a friend’s FB page with a caption that said the cob/core is a banana. I googled it and found the original post on Instructables.com.  The core is actually chilled sugar cookie dough. (There are egg free recipes) Marzipan is a great idea as well.
It looks like a “adult hostess” type craft the way its done in the picture and is probably too difficult for some of our clients/students, but it looks like it would be easy to adapt for a younger kid /special needs friendly version.
I am thinking you could have the child roll a thick log of dough and then have them smoosh it into the plate somewhat to use as a base to hold the candy corns.  Then the child doesn’t have to pick up the “cob” to work on it, and inserts the corn into the dough like it was on a playdough mat.
Any other suggestion on how to adapt this fun idea?  I think this would make a great centerpiece!