Let's try to save your son's halloween pics.
There are a lot of recovery software that you can use to recover deleted files - specially pictures. You can try to use Zero Assumption Recovery. You can download the software at this site: http://www.z-a-recovery.com/download.htm
It's a free software (you do not neet to pay to use this), and it's easy to use.
Here are the steps that you need to do:
1.) After you install this software, connect your camera to your PC (do not insert the memory card). Turn on the camera, open the Zero Assumption Recovery software.
2.) Click Next. Select "Recover images from the digital camera.." and click Next again.
3.) Select the Physical Device - select your camera , click Next. [grab a cup of coffee since retrieving the files may take some time depending on the size of the memory (",) ]
4.) After retrieving the files - select all the files that can be recovered. Click Next.
5.) Select the button on the right side (close to Destination) and select where you want to save the files. Click "Start revovering files".
I hope that helps.
Good luck and have a nice day!