If you're talking about the Folklorico Flowers, yes they're animated and move around (in a confined area).
Also no, I have not got the Donkey Cart offered in my particular treehouse yet. However, I can speak on another item appearing twice between a day apart from each other. It does not disappear after you buy it. I bought it the 2nd time it appeared as well as the 1st time, but it appeared again the next day after I had got the 2nd one the evening before. So far it's appeared 3 times now, even after I've bought / got all 3 each time it has appeared. There isn't any correlation/relation. I believe it's randomised.