There are dozens of cloud storage sites and scanner suppliers out there - I think Evernote would be happy to hear from any one of them, but they aren't going to adopt an individual provider and shut out the rest...
In terms of your general 'how to proceed' request, I think that's entirely up to you. If you genuinely have unlimited free storage from Raven, and you trust them not to lose your data, it looks like it would be in your best interests to go with them and not use Evernote at all.
If you want to add the extended organisational features that Evernote brings to the mix, I follow broadly what @PinkElephant has outlined above - I digitised a small library of technical information into several thousand pages of information that are (IMHO) far more accessible now than they ever were when occupying shelf space in a physical library!