Just woke up, and as it stands, dont see any possible way for a 70 to get the loot-filled pumpkin, as you need to queue for it, which requires 81-84, or so.
Quick how-to, Horseman kill: Get two 85s, one being a tank, they are grouped (without you), they queue for headless horseman, they get into the instance, have tank call for everybody to wait, tank gets lead, second, non-tank friend leaves, tank invites you, you either enter scarlet monastery or just click the teleport option on the mini-map, it's a simple fight, should be 4-mannable, just wait for them to kill it, done. Be sure to thank the other 85s.
And yeah, there is a pumpkin in deepholm, in the temple, theres two wings, one for alliance and one for horde, theres one in each, i managed to find all the others, including this one, lacking only the one from dragonmaw port, which seems to be phased.