What are the risks associated with taking a semester off while doing a Master's degree?
I know several people who have deferred their degree's at all levels for one reason or another.  In all these cases, the student has spoken not just to their professor but to the relevant department admin person and it's been pretty straight forward to enrol and pick up from where they left off.  None of them have suffered from taking time out.

I think you need to ask yourself a couple of questions so you can figure out which is the best solution for you.  Here's a few that spring to mind....

Is taking a semester out really going to solve your time problem?  If you will have the same issue again the next semester you enrol in then taking time out is probably a little pointless.

If you take time out, do you think you will stay motivated enough to re-enrol again?  

If you stick with it this semester, what can you do to generate more time?  You mentioned you travel to see family at weekends - is this something you can stop doing for the semester or is visiting an absolute necessity?