A few questions for a first Christmas
 

After a quick discussion with my son, I have the following questions (more "gift" oriented than "toy" oriented):

1) Is a standard green, tennis ball okay?
2) Are metalwork from a pet store okay? (If that's a maybe, what sort of questions should I be asking to ensure Knuckles' safety?)
3) What sort of toys have you've gotten your little guy/girl for Christmas on USA's Amazon? (I'm always worried when given general answers since wood treatment, plastics, and such can vary so much that a toy can go from "okay" to "hazardous" based on which one a person buys: Links would be appreciated.)