My recommendation would be to get a BSW then proceed with your MSW plans. Taking a GRE prep course would be beneficial if you went the LCPC route, but considering you've been out of academia so long, I'm concerned that you might struggle with the GRE. I'm presently in academia and found trouble recalling things I've learned within the past 5 years, but don't use regularly (mostly for the math portion). However, with that being said, when other candidates have really strong letters of recommendations from professors they've worked closely with in varying capacities for an extended period of time, the recommendation a prep course administrator could offer you wouldn't be very strong. The same would apply for a professor that you simply took a class with once. I had recommendations from one professor that I've studied with twice, my clinical psychology faculty mentor whom I've worked closely with for over a year and a former employer, whom I worked with for two years. By engaging in a BSW program, you would be able to foster relationships with faculty that would allow you them to write strong letters of recommendation.
Best of luck in whatever you decide! Also, look at programs you're interested in and contact them for advice. While right now you may not be competitive for more prestigious programs, you may still be highly competitive for programs that offer quality education and training, but aren't in the top tier.