Delta gives full credit (and miles, not dollars based) on the China Eastern flight. But China Southern would earn a reduced rate on Delta. I do not know enough about the .Aeroplan program to compare.

You can either call them to change the number if you wish, or do it at checkin time. And you can split between the programs if desired by having one number outbound and changing on the return. Might want to confirm at checkin regardless.

But what you should really focus is which program can you best use the miles on, and go with that if possible.