If you failed to heed my advice to snag a bouquet from a trivial Wrath-era dungeon before they finished updating the event, you will need a level 80+ character to farm one from the new Cataclysm five-mans. All of the other achievements are earned via daily quest tokens. My Warrior went from zero to complete inside of five days, and the holiday now spans a full two weeks. Some achievements, including the notorious candy hearts, are technically RNG dependent, but the threat is that you'll have to wait one more day, not that you'll fail to complete the event. I even snagged the previously RNG-only Peedlefeet minipet on my mage, which cost less than two days' worth of tokens.
(It's also possible to clear the event more quickly if you do a good job of getting stuff you need from other players and saving your soulbound tokens for stuff that you must buy for yourself.)
In the aftermath of the 2009 event, I speculated that Blizzard had intended for most players who attempted the Violet Proto-drake grind to fail, in order to keep the then coveted reward rare. Today, the pendulum has swung full circle; all the achievements I have tried so far have been quick and easy, and anyone who doesn't want to bother can simply buy the mount speed upgrade for 5000G.
Perhaps this reward should never have been attached to a holiday achievement in the first place, as it's arguably "too good" for the effort required today. Either way, world events in WoW are now much closer to the far superior ones in EQ2; fun distractions rather than stressful grinds. Limited time events aren't an appropriate venue for lengthy time investment with a significant chance of failure for reasons beyond the player's control.