W/Led and thinking of taking an additional quant course

Here is my situation and I would love to get some advice/suggestions...

I'm a R2 candidate and I've recently been W/Led at my top school of choice. I'll be trying to increase my chances of admit as much as possible by following the school's suggestions of retaking gmat (mine is mid 600s), additional ref letter, describing job promotion...etc.

I'm also thinking of enrolling in a Calculus course (as per the school's suggestion). Now, I did my undergrad in engineering but my grades were Bs and Cs in some cases for quant. Here is my question, would it be sufficient for me to enroll any local college/university or would it be better for me to enroll online with a recognized US university? (I'm a Canadian applicant).

Here is the course that I'm considering locally: (It starts in May and ends in late June). I guess the school really cares about these courses, they may give me a conditional admittance, pending my final grade?
https://postsecondary.humber.ca/courses/CALC_103.HTM

Here is a potential Berkeley online calculus course that I could take as well:
https://www.unex.berkeley.edu/cat/course597.html

Any thoughts or past experience related to taking additional courses while on the waitlist will be greatly appreciated.

Thanks in advance.