"There are three small children walking in the forest."
Translation:Metsässä kävelee kolme pientä lasta.
Apparantly DL corrected this. Either that, or they just have multiple versions ... xD
You can arrange the words in multiple different ways, but they're not all equally correct with a given English translation. Language is not simply the sum of all the semantic meanings in the sentence. Different word orders emphasise different parts of the sentence and are appropriate in different pragmatic contexts.
Metsässä kävelee kolme pientä lasta. = There are three small children walking in the forest.
Kolme pientä lasta kävelee metsässä. = (The) three small children walk/are walking in the forest.
Placing kolme pientä lasta first is usual when we are talking about a specific, known group of three children. Placing metsässä first lowers the topicality of kolme pientä lasta and means that we'd be more likely to use an existential sentence with there are in English as we're introducing them for the first time.