How to speak like a japanese child?

Question:

All I know is they say 'tan' Onee-nii' and 'Onii-nii' anymore? PLZ HALP D:

Answer:

Jeez I taught kids for 10 years and now have kids of my own. Never heard that. "tan" and "de-chuu" sound like a maid cafe oneesan trying to sound "cute" for dirty old perverts. Real kids would get beat up if they talked like that.
Kids refer to themselves in the third person, like if the boy's name is Makoto, he'll say "Makoto likes cherries," or something like that. That's one thing I noticed. Another is using "-chan." As you most likely know, -"chan" is kind of a cute way to address someone. Like oneechan for big sister, or even otochan for dad, and bachan and jichan for the grandparents. Maybe get on Youtube and look at some TV shows with kids--like Sazaesan , Doraemon, or Chibi Marukochan, (and Crayon Shinchan--which is the most realistic lol)---they aren't perfectly realistic, but listening to the kids talk in these shows will give you some idea.