Chess Tactics for Kids

My two sons love chess and to let them have a chance in some kids tournaments I encourage them to do some chess problems from time to time. I started with the Manual of Chess Combinations 1a by Sergey Ivashchenko which is really a nice collection for kids, but unfortunately the problems get harder fast. So volume 1a is doable for a kid of about 900 - 1000 ELO (DWZ in Germany) but volume 1b is already very tough (three and four move combinations). 

So I'm looking for alternatives. There are a lot of problem sets in the internet but most of them are not in the range I'm looking for. Polgars 5334 problems start with 300+ Mates in 1. Those were nice and solved in No Time, but after that already tricky Mate in 2 problems start.

Polgar's Problem #325, Mate in 2

They are mostly not about recognizing common patterns. They are about calculation and board control. If a kid enters a endgame with a king and a queen it should know how to mate at all and what a stalemate is and it should not start to look for possible mates in the middle of the board. 

So those problems surely teach nice skills but are not actually what I'm looking for.

One often recommended problem set especially for kids is one that a local coach (Paul Gaffron) assembled over the years. It is a collection called Tactics for School Chess. I started to look a volume 4 out of 12 and here it seems the difficulty is about right for my kids (especially for training of fast pattern recognition). 

Now I'm faced with a different challenge. I have those books as hard cover only. To load them into my training GUI I need them in PGN format.

I have an idea how to do it at least semi-automated. Unfortunately the first step, namely turning a printed diagram into a FEN that the computer understands, is a manual step. But if I have a collection of FEN I hope I can enable my computer to do the rest of the work. 

I'll give it a try.