If you are using red ants or other varieties that can bite keep your child a safe distance away from this part of the project. Capture as many ants as you can including a ant that looks larger than the others and a queen ant which may have wings. You might also scoop up little white eggs and larvae. If ants are not readily available in your area craft and hobby stores can generally give you information on where to mail order them. They are generally very inexpensive and travel well.
Ants like to east small bread crumbs, or bread dipped in sugar water or with a drop of honey.
They can also eat tiny bits of fruit and vegetables but don't feed them to much or their tank can get cluttered before they can remove it to their underground storage space. To water your new pets, let your child drop a water soaked cotton ball into the farm. Most of the liquid ants need they can get from their food but it is a good idea to add a new wet cotton ball every few days as needed. Your ants probably will not be able to climb up the glass walls of the jar but if there is a chance the jar could be knocked over it is safer to include a top with holes punched for adequate air supply. The added darkness can also trick ants into feeling they are underground.