Is this a good idea? for plans after high school?

I honestly wouldn't count yourself out for SFU Health Science, you still have a decent chance of getting in. Rarely schools cancel your offer of admission unless there is a large drop in performance. You also have the opportunity to bring your grades up again by the end of the courses as schools typically give final admission based on final grades, so study hard and possibly wait until July or August to know for sure if you will not be getting admission.