Localised programming languages
If your target language allows words to change their form flexibly (cases for nouns, tenses for verbs, AND words can change their endings based on gender. One example is russian), then localization is not a good idea, and it'll be better to keep keywords untranslated.
English doesn't have those features, and because of that it is nearly perfect for programming and technical documents. On other hand, any attempt to use Russian for programming language I've ever seen were reliably producing horryfying mind-destroying abomination that I'm certain aren't safe for children to even look at - mostly because words do not follow their natural behavior. Unfortunately to see the problem in action you need native-speaker level language fluency.
Otherwise it should be possible to either write code preprocessor or modify language directly. If source code for interpreter is available, you could modify list of original keywords.
Also, is there any language that would be easier for kids to learn?
If I remember correctly, LOGO was originally designed for such purpose.
Somewhere after the age of 10, some kind of BASIC should work. Any language can be used as long as it can be fun - i.e. you can draw something something on screen, make shapes move, etc. - as long as you don't delve into boring things like string comparison/traditional classroom tasks and keep things simple. It shouldn't matter that it is in non-native language, because commands can be trated kind like lego blocks - i.e. you place them around, without really thinking what they mean in english.
Below the age of 10 it is hard to say, and you might want to ask elementary teacher or research pedagogical books.
Another problem is that when I was a kid playing with programmable microcalculator, there were no widely available computer games and multimedia applications, so the graphics you could see in arcade were some kind of miracle. While writing a simple program that could slowly move a circle around, your code you could perform similar miracle. Nowadays, situation is quite different, games are available and assests used in them took a lot of time to create, so one person will have hard time "making a miracle" similar to the computer game they saw.
So, at current time you'll probably have to either implement custom graphical framework (2D) or search for something that already have it.