General help

My vote would be one system.  I use facetoface.  It is a third party plugin.  You add the activity to the course, they get credit when you mark them attended.  They can, once enrolled, "book" themselves (I rename this registration) for a session, it sends reminders, gives you a list of expected participants.  There is a 3.1 version available (new, and a long time coming).  We customized ours to allow attendance by ID, because most of our staff have ID numbers and it is just easier.  It can be a little fiddly, so work with it before you go live, though I have not seen the 3.1 version, could be improved.  Manual booking has always allowed booking without enrollment (an error, to my way of thinking), so you must make sure proper enrollment is engaged when doing that (would be great if this was corrected for 3.1!).