Learn something on the business end if you really want the minor title on your degree. I doubt it matters later (might as well push for double major) but the basic knowledge gained can be helpful down the line.

If you're taking classes out of interest, then take things for fun and not forcing a minor or anything. Less hassle and more flexibility to take supplementary subjects. If there's time free during the week, I don't know, find some work first before piling up on classes.

I suggest learning about something you are interested in.  You never know when your additional skill will come in handy.  interested in a foreign language?  Maybe in the future that will be the edge you need to work on an overseas project.  If you are interested in landscape or construction management, sure, why not get additional skills to put you ahead of the pack?  But I would say, don't overthink it.  School can be stressful and it's always easier to study something you enjoy then something you don't.  You won't get many opportunities to study for the love of learning with this intensity in the future (probably).