> Would EVERBODY know what a speaker was talking about if they used those two terms?

I don't think so; that's half the fun of it though - to work things out from their context. It's playful; you can coin your own, and you're never wrong! I don't think there's much of a worry that kids would only learn the rhyming slang terms, because the vocab. is very general, just common, everyday words which they'd pick up regardless which way.