I would be careful heeding or listening to much (if any) advice you receive on this forum. You are asking a difficult and complicated personal question that no one will be able to specifically answer for you, especially based on the limited info you've provided.
First off, as you know, you will have to take the MCAT to be accepted into SGU (or any other reputable Caribbean medical school). Ones that don't require them are a complete crapshoot. There's no way around this.
Secondly, medical school at your age is arduous... and really, really expensive. Unfathomably expensive right now. This not only in terms of time, blood, sweat, tears, and personal treasure, but also as a matter of tuition and lost income. Figure that, even if your plan goes well and you start at age 40, you will not be making any real money until you're 47-years-old at the earliest.
Lastly, you're not "advanced age", but the dream is just that - it's a dream. Whatever you perceive about being called "doctor" and helping people is probably just a romantic fantasy. The reality of what it means to be a doctor today (and even more by the time you'd graduate) is usually either being an employee answering to some bean-counter dictating about when you work, how you're going to practice, and how they're going to look at your metrics to determine whether or not you should continue to be employed... or you're going to be struggling through a mountain of regulations and insurance bureaucracy while continuously competing against those same corporations who are going to try to squeeze you out of existence with their midlevel practitioners and "more efficient" model of providing care.
If I was in your shoes, I'd strongly consider the old adage "a bird in the hand is better than two in the bush." But, there's also no reason you can't stay in school and prepare for (and take) the MCAT... "killing two birds with one stone", so to speak.
Advice is only worth what you've paid for it. Please especially remember that too if nothing else.
-Skip