I've been waiting to see if anyone would reply to this, in case they had anything more constructive to say than me, but no-one has - and I think the reason is, unfortunately., that there isn't an answer.
The language you've been asked to teach is not only too complex - it's also language that no native speaker child of that age would use. Everything you say about the language you want to teach and the way you want to do it is fine - the problem is the Chinese teachers.
What textbooks do they use? Are they aware that there are textbooks for that age group - no text (as they're not reading yet) just pictures and simple language activities - songs, games etc. Have a look here
for instance. I'd suggest you get hold of a book like this and show it to them, and tell them you want to base the course around it. If they say no, then I'm afraid that the problem is that they know nothing about teaching languages (from what you say, I wonder how much they know about teaching pre-schoolers in general!) Personally, I'd find another job...