I am reading a book which is very pro-organic foods…it is great on the whole.
The author suggests switching to organic fresh ground coffee, rather than instant…
I have found an instant coffee today which is organic (and fair trade)…I know that fresh is always better, but would organic instant contain any toxins that fresh organic coffee would not?

No, it would not, but instant coffee has always inferior coffee beans.
As to organic..it depends how narrow you put it. Just the raising of the crops ( as in toxins) or preparation as well. Since Instant coffee is highly processed some people would not regard it as truly organic due to the impact its preparation has on the environment.
But if you are foremost concerned about your health and the health of your children and decide one shortcut is fine…go for it.Enjoy your coffee