If the Restaurant has the budget a Yamaha Clavinova would be a good choice. It has 88 Keys plus Style accompaniment. It also has an excellent Acoustic Grand Piano sound plus many other excellent voices in it. It's loaded with features and IMO would look good in any Restaurant from upscale on down. But they don't come cheap. A CVP 309 GP is upwards of $6,000.

Best regards,
Mike
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Yamaha Genos, Mackie HR824 MKII Studio Monitors, Mackie 1202 VLZ Pro Mixer (made in USA), Cakewalk Sonar Platinum, Shure SM58 vocal mic.