If i had to pick one for a new guy jumping into RPG Maker, then I'd definitely choose MV.
Great resource & plug-in pool, great flexibility, easy to use UI, relevant scripting language and possibility to port to Windows, Mac, mobile and browser.
Now... for the long answer!
The resource pool for RPG Maker MV compared to the others is on a other level. This is in turn connected to being one of the later engines, but also due to the new scripting language as well as management of the resources (such as the plug-in manager).
New resources had to be made, and due to increase in tile size, new tilesets had to be made, meaning room for more detail. New scripts and plug-ins had to be made, and since it's a new scripting language, more people could make them as not everyone wanted to learn Ruby (RGSS3) due to it mainly being used in older engines.
Great flexibility is kinda tied into the resources and UI. I haven't really gotten into this myself, but due to the resources, and plug-ins you can alter things with MV pretty well, as well as the UI has a very clear overview.
Comparing it to other makers, it has less bugs. MZ is new and suffers from bugs that their still patching out. Another important comparison is that MV uses java script for coding. Older makers use Ruby Game Script System, which is an outdated scripting language in my opinion. Great, now how is this relevant?
What does this mean?
It's hard to narrow down just one specific interest going into a new program. Game design in general. It can be a one man job, but also several. I mention this because different people have different interests. Maybe they like level design? Perhaps writing is more on their agenda? Pixel art? Or perhaps they really love to script, actually creating the systems and foundations of their own projects. It's amazing what you can do if you know to script, and even if you don't end up with game design as a whole, it still opens up other paths for you if this is your thing.
Considering it's for kids you ask, i find it pretty relevant that you can port the game to Windows/Mac, Mobile phones and i believe it can even be browser based. The older engines can only creates games for Windows, no other platforms. The reason i focus a lot on this is that kids now days have smartphones better than mine, so it'd be pretty neat to have it on your phone to bring it with you.
Hope this answered your question to some detail. I might be wrong on some points, so if people catch them, please correct me. MV was primarily out in the years i took a break from RPG Maker, but remember this being part of the reason i picked it up in the start.