So, now it's time for the OP to tell us what scenario he *actually* described to them. Because this doesn't at all sound like "selling Bitcoins on my website."
Once again, the legal position of Bitcoin is very simple. "Money" is that which has future value. "Currency" is that which has current value. Bitcoin is a currency, with no guarantee of future value.
FinCEN regulations only requires that you transmit "currency, funds, or other value that substitutes for currency". Transferring Bitcoins to the buyer transmits currency (or value that substitutes for currency).
This has nothing to do with Bitcoin. Bitcoins can't be regulated, because they come with no implied guarantees of future value, no backing and thus no counter-party risk to regulate.
But *selling* Bitcoins has counter-party risk for the buyer. The seller might take his money and not provide him the Bitcoins. This is precisely the reason (or at least, the supposed reason) money transmitters are regulated.