I would take the public face of their website the same as I would their actual public storefront. Including a photo of a restaurant's storefront would be quite common in a review, so I wouldn't see any issue with a screenshot of their home page either.
Of course, it's a little trickier than that because their webpage can itself contain copyrighted material. For instance it could include a photograph of the restaurant that is itself a work of art and copyrighted as such. It could also include advertisements that might be an issue, though you would likely want to cut them out of a screenshot anyway. Even so, I'd think you'd have a good 'fair use' claim. Writing a review or critique is one of the fair use exceptions.
The name of the restaurant with a link to the URL would be fine for attribution. I'd probably include the date accessed as well since they might change things up frequently, or by season, etc.