Welcome, 4HiHo, to Apple Support Communities!
You appear to be concerned about using your new iPad mini with a Mac (MacBook Pro) running Sierra.
I’ve been using my iPad Pro (2nd gen.) with my MacBook (13-inch, Mid 2010), which I did upgrade to High Sierra, for many years with little trouble.
Sure. I don’t get the nice Handoff features, and the versions of Numbers, Pages, and Keynote, on my MacBook are significantly older than the latest versions that run on my iPad Pro, and my wife’s iPad Air.
The only “problem” was that once some of my Numbers Spreadsheet Tables exceeded the Column limits of the old Numbers version, I can no longer use them in the old version of Numbers.
Before that, I had no real problems switching back and forth.
You might have some difficulty with linking old versions of iTunes to your new iPad mini.
(I have heard of some people having some such troubles. I just finished trying it on my old MacBook. It downloaded and installed an update to iTunes. I now have iTunes 12.8.2.3 on my old MacBook, and can link to my iPad Pro. So I don’t seem to have that problem.
Note: the update dialogue box was up for what seemed like quite a while, and disappeared, while still claiming over a minute left in the installation. Then, for quite some time, I couldn’t start iTunes, because it was being “updated” [I could see update system processes running using Activity Monitor]. Once I saw the update system processes disappear from Activity Monitor, a couple of tries later, iTunes came up and I could see it linked with my iPad Pro.)
I haven’t used iTunes for updating, backing up, or such, with our iPads in a very long time.
So, perhaps, if you can express more about your concerns, we may be able to help assuage your fears—at least by reassuring you that we will be here to help you over any “bumps” you come across, on your “journey”.