My island is just 48" long and I have two Cree LR6 LED's over it spaced equally lengthwise and centered width-wise. My peninsula is 84" long and just 35 1/2 wide. I have two over it, but without the other lights in the room on, that would not be enough. Your island is a lot wider. You might need to stagger your lights depending on what other light is nearby. Look at the thread below - I posted pictures earlier - mamalynn.

Here is a link that might be useful: Recessed LED thread

mamalynn - Thanks for your response and the link. I forgot to say my ceilings will be 8 1/2 ft.

My ceiling is about 8 ft. That, the fact that you see the island, then look past it to the rangehood and cabinets, and that it is a narrow kitchen, caused me to choose recessed rather than pendants over the island. I thought they'd detract from the rangehood and cabinets and also feel "in your face."

My island is 48" x 84" including an 18" overhang. I personally don't like recessed lighting in our period house but wanted a functional kitchen. We're putting in four 4" recessed lights approximatedly 12" in from the long side over the cabinets and 10" in on the short side. (The lights will not be around the island but around the cabinets under the granite) We do have a chandelier in the center but the recessed lights are my working lights. We have 9' 4" ceilings. Placements depend on height of ceiling and size of of the cans. Remember the light comes down like a cylinder and spills out more the further the distance. I think I read somewhere for our room (height wise, can size, etc.) the recessed lights should be 36" - 42" apart maximum.

I think most people have 5" or bigger lights. I started with 3" but my architect talked me into 4" lights. I have 5" in the shower and over the laundry area where there was no space for a regular light.