You can with lead/contact view. I do not think you can add that button to Reports.
Why not just create a sales insight campaign for them to trigger? Or you can pull in the leads based on membership.
VP wants to empower them to create their own target campaigns. He wants the roll-up visibility to see what they're doing and how many emails they've sent. (We have no inside sales and an under-staffed Marketing dept so we seem to be turning our field sales into mini-Marketers.)
A button available under the Campaigns view would be a really great feature.
Just realized this can be accomplished on the Leads and Contacts view via Custom View. One of the custom view options is Campaign Name. Need to run the Marketo mailing for first Leads and then contacts, but at least it allows the mailing to occur.
Preference is still to have a "Send Marketo Email" button in the Campaign list and I have a feature request on that but this will acheive same goal.