Cool project and an interesting challenge.
The chances are, you'll be impressed at how well this child does, just because children are very efficient learners compared with adults.
Two pieces of advice which are related to each other: (1) make him laugh and (2) have a laugh yourself. Make these some of the first things you do. Everybody will relax.
When it comes to the procedural stuff involved in running a session, (including where to sit, what's on the table, who's entered the room, who's speaking to whom) replace the missing visual information with commentary. Include in your commentary what you're doing and what's going to happen next, to reduce stress and build trust.
When describing the pieces, let the child do the work. He's much more likely to remember something he has had to work at describing. Your role will be prompting him to improve and refine his descriptions. You might be reading this asking, 'how can he describe things he can't see?' Well, he 'sees' with his hands, and seeing via the sense of touch takes longer, so allow him time to look each time you ask him a question. In addition to that, I guess he'll need a chunk of time near the start of the session to look at the tactile chess board and the pieces, so you'll want to incorporate that in your session plan.
When it comes to teaching the moves, I reckon you could use the chess board directly. It will be possible to feel parallel lines on a tactile board such as the one in your photo. Same for diagonal lines.
And on the fact that you're new to this, remember: children love it when they realise that you're learning too. They feel safe when you take responsibilty for stuff that goes wrong, and they immediately forgive you when you apologise for a mistake, allowing you to move swiftly on.