V.B.
Balloons. Really. Use them as decoration, and then give one to each kid as they leave. Trust me.. most kids' parents do NOT want the kid coming home with a bunch of junk in a bag, nor candy, or even necessarily a less junky toy. A balloon is perfect. Kids like them. And they are disposable. They go flat by the next day or three and go right into the trash. No finding a "home" for it. No feeling guilt for not wanting to keep it. And no sugar. Kids get enough sugar with cake/ice cream/ drinks.
If you want, get a tootsie pop and tie it to the end of the string, both as a treat and as a weight to hold the balloon.
Gotta be helium filled though. :)