I need to upgrade to iOSX 10.6 Snow Leopard but have a nonfunctional disc drive. Can I download the software or get it on my computer any other way?

I gave my 2010 iMac to my father but it has a nonfunctioning disc drive (cannot read any type of disc). It's operating on OS X 10.5 Leopard. We need to upgrade him to at least OS X 10.7 Lion, but judging by what I've read so far, we cannot do that without first installing OS X 10.6 Snow Leopard. I cannot find a way to download OS X 10.6, and having the disc shipped is not an ideal option. Does anyone know of a way I can download a legit copy? Another option — though I'm not sure it'll work — is to order the OS X 10.6 disc, transfer the files from the disc to a USB key on my newer Macbook Pro, then bring it over to my dad and install it on his iMac from the USB key. Does anyone have experience with this who knows if it will work or not? Thank you!