Do you have a can or other lighting that will be directly over the sink? If so, then the lanterns are mainly ornamental, and I'd center them. If not, then they are important as task lighting, and I'd edge them toward the side where you will do work.

For a 9ft long Island, 2 pendants may be enough considering your ceiling heights. You'll want to space your pendant lights 24-inches to 30-inches apart. To space your pendant lights over your island, first find the center point of your island. ... The bottom of the pendant lighting should hang 30-inches to 36-inches above the countertop of the kitchen island. So, you don't need to place any directly in the middle of your island. Though it many be determined by the quality of lighting, I still think there will be enough illumination.

I am a tall person and based on celery’s rendition I’d have to put the pendants at a minimum of 36” above the countertop or it would hit my eye line and feel claustrophobic. Can your ceiling height support what you need height wise based on your fixture height? I’d be inclined to do 2 with a space / clear view over the sink (my personal preference).

I will have 10 ft ceilings in my kitchen, I am having them placed 36 inches above counter, since it is easier adjust it higher ourselves after we move in. I choose lanterns that will be sort of open also..

IMO pendants in kitchens should light the island not the ceiling so I would be looking for different pendants and as for placement that really depends on the pendants.