I think the previous owner is noted in the coin, so I guess the answer would be yes, it’s automatically done.
What complicates the matter is that there won’t be that many Safecoins, only 2^32 (4 billion and a bit) pieces. In fact, it is important that there should be not too many of them, because “farming” depends on their scarcity.
To go around that coins are not granular enough for everyday use, I think the currently favored method (which, as @mav mentioned, is still not finalized) is that the wallets themselves will store fractional coins. However, I’m not sure how the transfer of those will happen between the wallets. (Interestingly, as I was looking for this link, I discovered that another discussion started about divisibility just yesterday; I’ll need to get up to date on it.)
In the end, I believe you’ll want to go with @davidpbrown’s suggestion: you’ll store whatever you need outside the Safecoin transaction itself.