I've been thinking of getting the iPad mini 4 for the same use as you've described, but I've been too wracked with pre-buyer's guilt to buy it.I see them as work (12.9) and play (9.7). I have my 12.9 in front of me all day at work. It is my primary computer.
When I get home I use the 9.7 for all of my entertainment. I only get out the bigger one if I need to do something work related. I have gotten to the point where I don't even use my phone all that much. I use my mini 4 to watch the news and Netflix while I get ready for work in the morning and for reading before bed. I feel that each one serves a purpose and I am happy to have them. Obviously if my family fell into financial hardship I could let them go, but for now I am enjoying them.
I had a mini a couple of years back, and I kind of miss it, but I'm concerned that the 6s would make it redundant. Anyway... First World Problems, I guess.