At this point, the only thing upgrading those attractions would do is start earning $ and XP like a regular building. They don't give you anything special for Act 3. I don't think they're worth the donuts.
...The playdough factory doesn't say how to do the quest either.
The Playdough factory won't do anything until you finish the Act 3 Quest Line. The quest line is titled "The End of the Beginning". Just tap Maggie's picture in the task book. The quest line has 22 parts and most of the parts require 8 hour tasks (or longer) so it will probably take most people 10 days (plus or minus 2-3 days) to complete the whole quest line. Then, once you complete all 22 parts, the Playdough Factory will have a mini game you can play to earn a small amount of donuts for free.
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The Playdough factory won't do anything until you finish the Act 3 Quest Line. The quest line is titled "The End of the Beginning". Just tap Maggie's picture in the task book. The quest line has 22 parts and most of the parts require 8 hour tasks (or longer) so it will probably take most people 10 days (plus or minus 2-3 days) to complete the whole quest line. Then, once you complete all 22 parts, the Playdough Factory will have a mini game you can play to earn a small amount of donuts for free.