Welcome, Bellejack!
I'm no expert, but we have a kitchen island that is 6 feet long with a seating area on one side, all the same level because I wanted lots of workspace. Over the island we have 3 low-voltage pendants: one centered and the other two split the difference...in other words, 18 inches apart. Don't know if that's what a lighting designer would spec, but it's what our architect planned in our lighting layout. Sorry, no pics. You will need to think about what height to place those lights, eventually, with the two different levels on the bar. Also, consider whether you have other pendants in the adjacent rooms...too many hanging "things" can be distracting, IMHO.