You can use a trick of many email systems (Gmail, others) that I wrote about here:
You’d need to create an Asana account for each one, but you’d manage them all and all their notifications (if you set those up) will go to your email.
That allows you to use the Asana Assignee feature which is best. Other workarounds not requiring this “hack” won’t use the Assignee field so they’re not as good, but you could use Asana Tags or Custom Fields instead.
Hope that helps,
Larry