You don't get dollars for the large amount of choppings you have to do, so double them has no effect...
-Check your inventory and collect from the Coral Castle as much as you can! I get many corals and anemones for free as a drop!
-You don't have to do everything in a week! I started the first 24h boost today. I had enough energy this morning and enough time to play to chop the 20 corals in a day. And after that I'll wait again. I start the next when I have enough time, energy and anemones for it (or the coins to buy a few to get all needed).
-We'll get 250.000 coins after chopping the 20 corals in the first 24h, I see. So I guess we get some coins to help for next quests every time.
-Try to get more coins from coingiving things. I don't have any problems getting coins, and I only collect from things that also give me other resources. But I don't hurry to do this quests. Mostly because of the needed energy. But also because I don't want to buy things that will drop for free if I wait. Oh and 2 trades helps to get coins too!