Thanks for the advice everyone
And keep it coming. I find teaching quite a challenge but it's something I'd like to get better at. All of the advice you've given me is very useful.
I'm not done yet. Last week I provided them with masses of pictures to look out and I asked them to pick out the ones they liked and I asked them to say what it was they liked.
Then, mercifully, the cameras and the films arrived and I let them go to it. One of the other exercises I did was pick out pictures and then ask them to come up with words. When they got the cameras I then suggested that they think of the word to describe what's in the view finder. I get the films back in a couple of days so I'll see what they came up with. Can't wait. The printing advice you've given me will be very useful.
Thanks again everyone.