Oh, I vote for two sinks, one in the island. But my island didn't have a seating area. I had the big cleanup sink on the island and a small copper sink in a black walnut butcher-board countertop. The tree came from the back year when we cleared some of the property. If you are going to have seating, I would use the island for prep, maybe put the coffeepot there, but not a place for dirty dishes or grease spatters. I didn't put the stovetop in the island because I think it would have been too much trouble to clean and I don't trust the big fans to suck up all the airborne grease. I stuck it on a wall, sandwiched between two full-length wall cabinets with a small counter with drawers under on each side, and the updraft fan over there. We moved, and I so miss that kitchen.
Good luck with your renovation.