Since it's what I normally use for myself, I would use True Image 2013 or True Image 2014. You can usually get it on sale for $19.99 if you look for it and wait. There are others that are free, but I haven't used them. Since I use it for image backups, I can't take chances and must have something I can depend on, and True Image has rarely let me down.
I would install Windows 7 on one machine, let it patch itself, but do not supply the license key. You should be able to install it without providing a key and it will run for 30 days. Then install your imaging program and make an image of the system drive. Then you can use the imaging-software-provided boot disk to restore the image to each PC, and provide the license key for each PC and activate them one at a time.
EDIT: Of course you would make your first system image to an external hard drive, and use that to Restore the image to all the other PCs.