This is the right way, only I would reword it to “I want to visit your museum but I’m unable to use the app due to disability, would you mind taking cash or deb

This is the right way, only I would reword it to “I want to visit your museum but I’m unable to use the app due to disability, would you mind taking cash or debit?”. Try not to start conversations in the negative. You’ll get a lot farther.