I think the term nanobitcoins is a good one, but it should not be used unless/until the base unit of Bitcoin is made smaller. Otherwise, there will be a regular new FAQ: "I want to send someone a nanobitcoin but the system won't let me".
Still, even today it's hard to send 0.001 coins ("the system won't let me", sort of) and it's okay. So perhaps an inability to send a nanobitcoin will just as easily be accepted.