Hey Matt,
Yes, this is possible. If the rep creates a List view within SFDC, at the top will be the "Send Marketo Email" button. They can select any number of Leads to send an email to. When they click the button, they will be taken to the same interface as if they were sending one email. They can select a template, make any modifications, test, and then send. The tracking will show up in the Email tab of MSI. If you want it to show anywhere else, you will have to set up some smart campaigns. For us, we create a completed task because the rep is handling the blast so they should get credit for the activity.