I would assume you can get the mounts from the bonus roll too, as it's essentially another shot at the bosses' loot table. That said, it's hard to be certain, as I haven't seen either of these mounts at all. Drop rates seem to be abysmally low :-)
Wrong, Sha of Anger you can only receive loot from once a week, where as Galleon you can use it multiple times due to being a "Rarer" world boss than that of Sha of Anger.
Believe they also hotfixed it for Sha of Anger where you could use coins even if you had already killed him for the week.
I killed him twice this weekend on US realms, and had the option to use the coin both times. Same thing with LFR, killed the first and second boss, group fell apart on the third so I decided to come back later, killed the second one again and had the option to use the coin.
With all the flip-flop hot fixes, I don't know what to go with anymore. They took away the ability to use multiple coins, then they increased his spawn timer, maybe they put the multiple coin uses back in? I killed Sha during the week, forgot I had done it when my guild wanted to kill him over the weekend, and was able to use the coin again. Maybe it only counts if you actually use the coin? I didn't use the coin on the first kill, I was saving them for LFR (which was a stupid idea.)
I can confirm that as Galeon has 72h minimum respawn time you get a normal loot (+bonus if you decided to use the coin) each time you manage to get him down. Guess that's the sole reason why x-realm zones don't work in Pandaria.