Do market your business based on convenience, competitive prices, and most of all your commitment to value-added customer service. Do offer a private counselling area. Don't shout at seniors who may be hard of hearing. They value their privacy and don't want their condition blared out to other customers. Don't have entrance and exit doors that are too difficult for seniors to open.
Automatic doors are best.
Don't clutter up the prescription counter. Older folks in electric scooters may not be able to see you above the jumble. Don't offer a loyalty program unless benefits and rewards can be attained quickly. Seniors, like kids, tend not to think months or years in advance. Don't make signage and shelf-talkers too small for seniors with eye problems to read.