First aid kits are for employees, and the contents of those are not the customer's concern.
Having worked retail in many different places, I have to wonder what you are basing this on. IMO, first aid kits are for anyone who needs them. Every retail place I ever worked had one, and they were most definitely NOT just for the employees.
I think there's an important distinction (and others may disagree) in that employers provide first aid kits to employees as an obligation, but to customers as a courtesy. I'd welcome feedback about its contents from employees or my risk management team, but if a customer tried to make a Scout project out of something I share as a courtesy, I would not be receptive. Polite, but not appreciative.
If someone is injured in your store, do you think it's merely a "curtsey" to help them tend to their injuries?
Not to get legal, but I'd see it as a liability. Unless my staff are trained medical professionals - which most retail employees are not - I wouldn't officially want them to do anything except offer to call a medical professional such as an ambulance, and perhaps offer the use of a sink, or offer a seat.
I say "officially" because I wouldn't mind if a staff member offered a bandaid, but it would never be the official written protocol.