Last month I spent 75 bucks on people in need or appeared in need from gas in their cars to just plain cash. Did they truly really need it? It didnt matter, I gave it. Hope it made a difference in their day.
Of course it made a difference in their day, ya big marshmallow - but I hope you will set a limit on how much you can afford to share before joining them.
It IS hard to say no or ignore them and whether to give is a question I decide every time it's asked - usually it's no, but I have given money and food to some who seemed to truly need help.
The "I work for a living, so can you!" side is constantly at war with the "Sometimes people can't help needing help" side. Sigh. 
And then there's the other conflict: you don't want to see decent people suffer, especially when kids are involved, and you realize that the economy is so bad that we could be next, BUT, otoh, the more we help people in truck stops, the more people we will encounter in truck stops who will be seeking our help. Make it known that truck stops are the places to beg, and pretty soon, you won't be able to walk from your van to the building without being swarmed.
An ugly situation that nobody knows the way out of.