Have the latest iPad Pro, Pencil 2 & iPad Mini 5 but...

So you have both iPad Pro & iPad mini with you just so that you can charge the Pencil 2?

Best you buy Pencil 1 for your new iPad mini

Or feedback to Apple here: http://www.apple.com/feedback

Your iPad mini 5th generation got no way to charge Pencil 2 whereas the iPad Pro 3rd generation can.

It only works with the iPad Pro.