Cress is lovely to grow at home with children because it grows so fast! No long wait to see the seeds sprout. Within a week you have something that you can eat. No need for soil – I used an egg box, some tissues and the seeds.
Seeds, egg box lid, tissues 
Add water to the tissues to make them damp 
Put the damp tissue in the egg box. Place the whole thing on a plate 
Sprinkle on your seeds liberally. Help children with this step. You don’t want all the seeds poured from the packet in one place 
Place the seeds on a windowsil and keep them watered. The paper wants to be damp 
After a week you will have cress! 
To eat – cut as you need for salads and egg sandwiches
You could make a picture diary of this process – either take photos or do drawings. If you water the seeds at the same time each day it becomes a nice little ritual either at tea time or snack time.
(If someone in your family is allergic to eggs use a different growing container)