Get written permission from guardian of children in photos - all of them, so pain in the bum, but needed. And then register on istock photos. That's where I get my images from. All sorts of stuff on there... Fantastic resource. Then he gets £ each time someone downloads his image. he could maybe pay it back to the dance group / person???
"How can he increase his sales - people want electronic copies but he feels he cannot charge very much for that - smaller photos don't really take any less time to do"
Don't really understand this bit.
Photographers usually charge more for digital files to cover for loss of potential print sales, so he should probably charge whatever the average print sale for each image would normally be, ie, £30 if he normally sells 3 prints per file, and so on.