I'm not convinced that using different names is a really helpful idea. It requires an extra transition later on. Well no real harm done. But I wonder about the principle behind that: Dropping complexity because it is hard? I agree that child directed speech is different. It is simpler. But it isn't wrong. Couldn't you have said "the cat meows" or "this toy meows" or even "it meows"? That would have placed the verb in the right place in a simple sentence. The baby can now validly repeat the sound/word.