Hi Angela:
Well, there's no right or wrong.
I think extra credit given in substitution for assigned work is unfair, subjective to grade, and skews the class grades. EC is about points and grades and less about learning.
But what you describe is available to all students, is graded the same way, and begins at the beginning of the course. I think this is a sound grading practice. It's similar to dropping the lowest quiz score.
Regards, Barry
