Magnetic
An alternative to using attachment constraints - use magnetic 2.1 to attach mesh/poly objects to the surface of another mesh object using the painter interface or a guide shape and each attached object will retain its position and orientation respective to the surface as the surface is animated.
new features in magnetic 2.1:
1. automatically align attached objects using the guide shape's local z-axis
2. ability to position/orient objects without applying a transform script controller (for target surfaces that will not be animated)
3. upgrade attached objects from magnetic 1.5 to magnetic 2.1 functionality
Snapshot of 2.1 interface: 
Snapshot of using a shape as an attachment guide: 
Snapshot of using the auto adjust feature to evenly distribute objects along a guide shape: 