Others here have suggested that lenses are not the issue, but maybe lighting is more important. They are closer to the truth about this subject. Of course you need the proper lens, proper lighting, proper styling, but, most of all, you need a talented and experienced shooter, if, as you said, the results are critical to your family business' success. Perhaps you could eventually be that person, that photographer, but, if you need to get your pictures sooner than about a year from now, and if you cannot afford to spend hours and hours, weeks and weeks, practicing, learning and improving yourself, perhaps hiring a professional is truly your best option.
I am not suggesting that you hire me, but take a look at both my food portfolio and my people with food portfolios - only two of the 15 portfolios on my website - to see some good examples of food oriented images shot mostly for high-end editorial use, plus some for advertising type use. This will give you an idea of the road you'll have to travel in order to "get" where you'll have to be to do it yourself. I think you'll quickly understand that your best bet is to hire out this job. You can see my website information at the end of this post. Meanwhile, you can work on your skills and, hopefully, some day do the job properly yourself. By the way, there is no best lens, but the TS 90 is probably the most likely overall candidate, depending on multiple factors too numerous to get into in this forum post. Good luck to you.