What mammac5 said.^
1530 is way too early to be checking FSBS. If that's the time your facility chose, you may need to become an advocate for changing it to 1630 or even later, as the short- and intermediate-acting insulins should never be given more than 30 minutes before a meal and preferably no more than 15 minutes. Since you have only three diabetics, you actually have the luxury of waiting till suppertime to do blood sugars and insulins together; when I was working LTC I routinely had ten or twelve, and it was always a mad scramble to beat them to the dining room and get all their DM care done before the meal.
Even with that many, I'd wait till about 1645 to go around and do the accu-checks first, then come back and give insulin before my unit's trays came out around 1730. I timed it to where I'd start at the end of the hall and wind up near the dining room right about the time the food cart arrived, so I'd give those residents their insulin right after doing their FSBS, then head down the hall as trays were being passed to the rooms. That way we didn't have so much lag time between accu-checks/insulin and food consumption.
Even with the best of intentions, though, strategies like this can fail. We had one resident who was so brittle that his sugars could jump from 50 to 500 and fall to 50 again---within an hour depending on how we responded to it. And you didn't EVER want to give him insulin before he'd at least gotten a few bites in or he'd bottom out and become unresponsive, and you'd have to run for the Glucagon. Forty-five minutes later he'd be upwards of 350 and climbing........yep, he was a challenge!
Good luck, and good for you for asking questions. We're happy to help where we can.