This sounds like a great project and I hope that you are able to achieve your goals, what an improvement for your community this could be!
I don't know if you aim to achieve the full ADA checklist of accessibility, what materials or equipment you have access to, but at its simplest, the path should be wide and stable, firm, and slip resistant.
I would still want to make sure that your slope and cross slope are as minimal as you can make them, possibly by adding switchbacks, and add defined edges and turnouts, rest spots, etc. How is access to the start and end of the path? Try to think about downpours, ice, users who might have crutches, kids navigating the area with heavy backpacks, younger siblings or older family members, community members coming to access the garden if it becomes a feature, things like that. If you can, talk to your neighbors about their needs and wants, which can have the additional benefit of getting other people interested and supportive, and help with sourcing materials or other things you need.
You might find some inspiration in the garden of Stephen Cantu, who has a permaculture orchard on a slope in San Diego that he has designed to be wheelchair accessible and has created something called the FIG (Friendly Inclusive Gardening) program. I believe he uses crushed concrete or other road material, compacted and topped with 2-3" decomposed granite with a binding agent on top for paths. Videos
1 2 linked to where he talks about his paths, and garden design process.