Computer science degree vs. post-bachelor computer science certificate
There are two issues: whether it will be a formal barrier (i.e., you'll be screened out before anyone ever looks at your application carefully) and whether it will impress people.

For graduate school applications, there's no way you'll be officially screened out for this reason.  There are several programs aimed at encouraging post-baccalaureate certificates to help women enter computer science.  They attract excellent students, so grad schools are happy to see these applications; furthermore, if any grad school ever turned down applicants with such a background just because they had no "real" degree in CS, they'd be in big trouble on gender equity grounds.  So you have nothing to worry about there: grad schools are aware of these certificates and willing to consider applicants with them.

Of course, there are still issues of people's personal reactions, for example how rigorous or extensive they think the program is.  It presumably depends on the program, and also perhaps on which courses you take within the program.  If take you challenging courses and do well in them, ideally do some sort of project with a faculty supervisor, and get strong letters of recommendation, then you should be in good shape for grad school applications.  As a sanity check, you should ask about the placement record of previous students in the program: without some reason to think otherwise, you can expect you would end up somewhere in that range.  If they all do well, that's a very good sign; if some but not all do, then you need to make sure you end up in that top group.

As for industry, CS hiring is much less credential-driven than some branches of engineering (where there are more regulatory or liability issues).  If you can demonstrate talent and skill, then nobody will really care what your degree is in (except sometimes for research jobs that require a Ph.D.).  There are some tricky issues: for example, some of the top tech companies get enormous numbers of applications and have to filter them rather brutally.  However, even there the filtering is more often by prestige (did you get impressive grades at a top university) rather than the field the degree is in.