I wrote this children is walking instead of going .I do not agreed with this translation. On idzie means that he is going by foot .To go means that you go with any type of locomotion but in polish it's well indicated how you are going(by foot ,by car or something else .In that case it mans that this children is moving by foot so he is only walking.I'm sure that ids means walking and not going .What do you think ? Thanks for your answer .
If your sentence was marked wrong, this didn't happen because of "walking" (which surely is correct), but because you wrote "children" (plural) instead of "child" (singular).
I agree that without any context "walking" sounds better than "going". However, both are correct translations.