Take a flash light and go into a dark room. Put the light against the egg and look and see what you can see through the shell. Completely dark is a chick. It may not be alive but you will know if something is in there or not. There have been chicks to hatch at day 25. But with oiled eggs I can't tell you what you will find.
If they are clear go ahead and pull the plug. If they are dark wait a couple more days.
The best candler I found was a mini "MagLight" flash light -- it can even be adjusted to get a nice, tight beam of light going into the egg. Candling will add to the educational value of the experience for your daughter, and the addiction for you.
If you go back to the local farm, ask the woman if you and your daughter can collect the eggs one morning. That might add a little fun for your daughter and you can make sure the eggs you're taking to hatch never see the kitchen sink.
I use a Maglight too. If they are not fertile, or never developed, you willsee right through them. If the light does not pass through, then some developed.
Candling would have caught those clears at day 6, or day 14 for 100% sure. Good luck on your next batch. I use a surefire 6p with led upgrade on it. It's an amazingly bright light and you won't even have to take the eggs out of the bator to candle so no risk of dropping anything.