This is not too difficult.
1. Try to get alot of the more expensive Pinata. Elephanilla, Chewnicorn, even things like Fizzlybears and Horstachios will work.
2. Then buy them accessories - buy ALL of the animals as many accessories as possible.
3.Feed them each a Joy candy, or enough happy candy to make them as happy as possible.
Should unlock pretty easily. I think when I got this I had a Pigxie, Swanana, one or two Elephanillas, a couple Cinnamonkeys, a few smaller random Pinata, most had accessories, and there were a few pinata houses as well.