Hello Ducky... (sorry I had to say that
[it's a UK joke folks])
I still have and use my K-50, and really appreciate it's size. I bought the K-3ii for it's many features when my K-50 was in for repair (I broke the front casing) and it took a looong time. Otherwise I would probably have traded and now I'm glad I didn't have that option as I still enjoy using it.
I found that the lack of AA filter and higher resolution of the K-3ii made a difference to the images I took.
The shot below was hand held, in great light at 135mm on the 18-135, you know the one that's supposed to soft at the long end. It's straight out of camera too. Zoom into it and keep going and it doesn't fall apart at all, even the corner with detail is decent. I was very pleasantly surprised.
Get the KP because you want it anyway, and keep the K-30 as I think it will be worth more to you than the trade in value. Get your wife to shoot with the K-30 and we'll see you again when the conversation turns to her now owning the KP and should you get the awesome K3iii. Then we'll repeat..