Have just one A-sign on the ground that reads “No, we don’t want your money, they want your money” with graphic pictures of a mob of children that is recognizable from previous commercials. Then, you’ve disclosed that you will be asking for money, but also where it’s going. This A-sign should have scaled pictures of the kinds of things that the donator’s money will buy the child such as food, medicine, clothes, etc. Have a picture of a child, to leverage the propaganda of their commercials already making an impact
If there were a high pole raised above everyone with tied items to it and a banner that read, “what if your child didn’t have these?” then people would directly understand that this is an organization trying to get these tangible things to children in need, not just manipulate money coming from a leisure shopper.
If someone wearing a super hero costume approached you, you would light up and you’d be ecstatic. Their introduction would be a little different:
The point is, soliciting in a (non-ridiculous looking) superhero costume would get people much more excited about talking to a rando on the street. After their donation, the layperson can walk away with a souvenir cape to tie around their neck that reads, from the back, “I saved a child today. That’s MY super hero power.”
People like free stuff. Organize a free cape give away. Make a display that people want to come up to in order to become a Superhero. Attract the layperson with a “Superhero Transformer” portal with an overhead sign that says “Superhero transformer” that implies that when you step inside, you’ll sign a contract, and become a superhero for saving a child’s life.