Dear AJ,
Remove global variables from Child package, child will use the parent variables if you refer inside if Child which are declared in Parent and assigned values either in parent /child.
Same approach in DTS / SSIS
Parent : declare one global variable
add script task, assign some value to global variable
add execute package, call child package
Child : DON't declare any variable
Create script task, print (msgbox) parent variable
execute parent, you will see parent variable value in child.
Do not select inner/outer variables for this above example...
Regards
RB