I think you're misunderstanding. The overall GPA isn't going to be the end all for your application, as long as you can show a significant upward trend over the more recent semesters. For me, my circumstances that cost me in my first few years were taking care of my parents while they died of cancer. That's something outside of my control that admission committees take into account, but if that was the end of my story, I wouldn't have had a prayer. They saw me come back from that and carry a strong GPA for the last couple of years, and that's what impressed them.
Are your grades worth giving up over? Absolutely not. I do think that with all you have going on anyway, and the fact that you acknowledge the fact that you tend to struggle academically, taking 19 hours just to force a May graduation may be unwise. You could cut back some hours, really focus on the classes at hand and do much better than the aforementioned circumstances would allow, and take the other classes later (summer or, if you don't get in this cycle, the fall) and graduate later. It would be essentially the same use of time, but opening up the possibility for you to really shine academically and show them what you're capable of.
On the other hand, if you're really set on forcing the May graduation, you'll have to try your hand with the ECs and hope for the best. It's not guaranteed with either method, but you know your circumstances and what you can do better than we do. The grades are the more likely way to get accepted, but if you know that won't work for you, you'll have to work some other way out.