Hey brother;
I have struggled with these issues a lot too. I have had several unbelievers give me money.
Here are my conclusions:
--I do not know their hearts. If they express a desire to try to have a donation to a preacher boy or a gift to a church be meritorious then, of course, I would refuse.
---Many folks in your own church that will give are headed to hell.
--Most times people give it is not trying to merit anything but it is an expression of a heart of compassion - and even unbelievers can have this.
When you move into a neighborhood, many a neighbor (at least in parts of Missouri) will still make you cookies, etc, It would be very rude to ask first if they were unbelievers.
On birthdays and Christmas unsaved family members will give you presents. Do you refuse these as well.
--Also, in practical execution, how would this be done. Knock on the door and ask someone if they believe or not. If yes, okay, then you can give. If no,, then sorry you are not qualified to give. I can so no good coming out of this.
--Also, the children of Israel took gold from the Egyptians. We can use the money a lot better than they. Many a Hebrew has profited from foreign gov'ts of heathens and even served in their courts.
---The purpose of the project seems a generic humantiarian relief mission and not evangelistic. Rank unbelievers can help the poor too. I am even glad Angelina Jolie is adopting little kids from Africa. And my unsaved neighbors can certainly do their part.
I don't think that we shoudl refuse these acts of kindness. Too, it builds a relationship and an opportunity to tell them the Gospel because their interest will be peaked at how the trip went afterwards.