idea

Put 3+ types of seeds in a cup(s) and bring it to RS or put it on a table somewhere?,
Bring it back every week until it shows edible food, leaves, fruit.
or when it gets too big, maybe they will let you leave it at the door. :)

 smaller ideas:

Green onion, parsley, celery (leaves are awesome so need need to stalk it), basil !, spinach, lettuce
mini peppers or banana peppers, cauliflower, broccolini,  cherry tomato
carrot, beet (get a kick out of the 36(?) seeds per seed), potato...,

Many people have never seen the plants. It takes the fear out.  (I have yet to do this idea though)
seeing it take shape and how to harvest gives a visual, tangible understanding/goal.

My favorite farmer's market farmer was a city boy who grew a bean in a cup at school.... and it changed his life... now he has a huge acreage of crops with the farmers market as just a part of it.
 a bean in a cup can make a difference :) 

The language of soil ...and food from soil... is universal.