This is a wonderful idea - I especially like the aspect of making it more affordable. Do you see this as a tour-type program? Where the same chefs/waiters/staff travel to different cities? Or more permanent locations in multiple cities? I think either could work, would just be different models. One important factor to really build buzz around this would be to have local media outlets come and have the 'Dine in the Dark' experience and then spread the buzz through social media, newspapers and other sources. This would get people even more excited about the idea. You could also feature some of the chefs/waitstaff on a centralized website, highlighting their culinary accomplishments to build their reputation. I really like this idea and I hope to see it soon in my city!
Assuming the user has a mobile phone and data access, a search feature would be a good way for persons with disabilities to find places that have certain accessibility. For example, a person who needs wheelchair access and wants to go to a park can search for local parks based on where they are. One important key is the initial data entry and user acquisition to determine which parks, restaurants, spaces are more or less friendly for people with disabilities. Once that is up and running, the usefulness of the app will truly become more realized. Also, its important to note that (of course) not all people with disabilities need the same accommodations, so being able to sort by the specific accommodations/accessibility needed is imperative as well.