I would also consider public relations opportunities to spread the word on the amazing work you are doing. Perhaps there is a local media (newspaper, radio or television) organization that would be interested in sharing information. There’s no harm in calling … the worst they’re going to do is either say no or not call you back.
I would also think about leveraging your network and various different types of adjacent partnerships to promote what you’re doing. Is there a large local business who would benefit from announcing or promoting what you’re doing to their employees, can you work with the companies who are providing the products for your boxes to promote on their social media channels, websites etc?
Paid social works too, of course, I’d be really focused and targeted with your spend on this front to ensure you are maximizing your budget. Who is the audience you want to reach, and what is the most compelling thing they need to know about your offering? Ensure you’re hyper-focused on these people with you social budget for the best return on your investment.
I hope this helps~