Nobody can tell you what to do, as this is ultimately up to you and your family. That is a difficult situation to be in, and the decision cannot be taken lightly.
If you weigh your options there are several things to consider. One, by deferring to a later semester, you can work and save money while contributing to family expenses. On the other hand, the amount of money earned once you graduate would be much greater than the money earned during the deferment. However, school will take 4+ years, plus a residency which could range anywhere from 1 to 6 years. Then you're talking 10 years until you can contribute significantly at a maximum. Thinking this far in advance is probably not the best mode of thought. On the other hand, the job market is pretty tough right now and finding a good paying job with benefits is going to be hard to come by for someone looking for short-time employment.
I can only offer what I would do in a similar situation. If I were to lose a parent to an accident or health problem, I would probably leave school. But I have a bachelors degree and can more than likely attain a fairly decent paying job. However, the likelihood of coming back to finish my M.D. is pretty slim. I would think its best to start when you know you can finish and not try and complete a few semesters here and there. It will be of greater benefit to work all the way through.
Ultimately it is you and your families decision. I dont think anyone would fault you either way, because in both instances, you would be doing something to help the family - whether that be in the short-term or long-term. I wish you good luck in your choice.