I don't think it's creepy at all. Some people just have a giving nature, and love to help out others. I think it's wonderful of the couple to do that for the little girl.
Whether the little girl wanted the stuffed animals or not, she was willing to sell them to buy herself something with her own money that she'd earned herself. I think that is a valuable lesson for any child to learn, and I'm sure her parents probably were thinking the same thing. She was willing to do that, she took steps to sell them, and the strangers probably admired her for it. By giving her the money, they were just rewarding her for trying to earn the money herself, which you sure don't see a lot of these days.
They most likely took such joy in seeing her take it gratefully and thank them for it. Why rob people of that--isn't there enough selfishness in this world that we should appreciate when someone is acting just the opposite?
How many of you haven't done something like that for someone? Maybe not money, but a kind gesture for a stranger? I'm sure most of us have at one time or another... :)
Also, as far as the supposed wrongness of her selling her things in the first place...I don't see how that is so wrong. Many, many of us have held garage sales to sell our unwanted items, haven't we? Or have went to other people's sales and bought things. What's the difference?