The iPad Mini 4 hasn’t been updated in several years, but if you like the size, you can save a ton with today’s refurb deals on Amazon. Get the 128GB model for $250 ($150 less than buying it new), or the 64GB model for $20 less.
The iPad Mini 2 is practically a fossil at this point, but it can run iOS 12, and in fact, the latest OS actually made it run faster than iOS 11. It’s also down to $140, also refurbished.