[big green bloke]

any ideas what veg the children could grow in the winter time that is easy as they are only about 4-8 years old 

[Swing Swang]

Where - Outdoors/unheated greenhouse/indoors?

[solway cropper]

Sprouting seeds are a great introduction to growing things for kids as they show very quickly and taste nice. You'll not get much else to germinate in the winter.

[Aunt Sally]

Cress should grow indoors too.