A quick calculation (this will probably be wrong) is that you need 36 tokens for this food required for this quest, 30 of those for the 5 of each feasts and a single one to create the food required for the quests. Without trading in Spirit of Harmony for tokens it seems this will take over a month to complete.
Food is tradeable. Assign one character as the guild chef, and have all the other players funnel him food from their farms and from trading in their tokens. You get something like 13 tokens just from the initial quests at Halfhill, plus you can grow 20 or more vegetables per day on your farm. A player with a few 85 alts can easily farm up 40+ tokens in an hour or two just by taking each of his alts to Halfhill to do the opening questline. This is a one-shot deal, of course.
That said, you're looking only at the mats required to make that food. It takes considerably more to level cooking to 600 in each Way, which is what you'll need to do to learn all those recipes.
Of course, you can also farm up the food in other ways. Tokens and (literal) farming are really the only efficient ways to get vegetables, but meat and fish can be obtained reasonably efficiently in other ways. Save your tokens for vegetables and farm the meat and fish the old-fashioned way. And there's always the AH, of course.
Alternatively, you can outsource the cooking of the feasts to a chef outside your guild. Spam trade for someone with the recipe and see what he'll charge to make them with your mats.