We have and love this swing (in less obnoxious colors). I had a friend who sews make big cushions for the back and sides; you could literally take a nap out there in summer...I may have actually done that a time or two. :)
Consider having a Jonah figure be on the end of the string. Make as a classroom activity at the end of class, or if's you're adventurous, complete most of the construction and have the students finish for their own take-home came.