What you should do is place the pendants absolutely centered on the island but place them 1/3 of the way in from the seating area. Then place a high hat directly above your sink for good task lighting. That's what I did and it works beautifully. Those sitting at the island get good lighting and you working at the sink get good lighting and no one will ever notice if it's slightly off because no one ever stands exactly dead center looking.

how much space between the pendants. Ann, in both comments I mentioned a guide up in my first comment. I guess you keep missing it? here it is again,,,with 3 others. these should give you the needed spacing to choose pendants. while you can play around w/the distance between them, the height should be right at 30" or so, with no more than 36" from the countertop. Since you're going smaller, you don't have to do the 30" between. smaller sized pendants can be a tad bit closer 7" is a mini pendant and far too small to use over your island. shoot for 10-14"

Go with 3, unless the 24" pendants cast a very bright/wide light. Spaced correctly, I think 3 would look more balanced on an island spanning 10', with little liklihood of casting shadows. Try suspending cut up boxes over your island to better visualize 2 vs. 3 lights.

My ceilings are just under 8' and I have a tall husband worried about bumping his head on pendants lol. Our island is 9' long but only 40" wide. We went with clear pendants so visually they weren't intrusive. Played around with how far off the island and found a height that worked for us (my husband). We originally tried the smaller 6" but in the end got the 10" version of these from PB: https://www.potterybarn.com/products/pb-textured-glass-pendant-hood/?catalogId=84&sku=3564536&cm_ven=PLA&cm_cat=Google&cm_pla=Lighting%20%3E%20Pendants&region_id=658780&cm_ite=3564536&gclid=Cj0KCQiA6t6ABhDMARIsAONIYyyT9EKIF7j5Z49P7maicy8XKMtK8CfyevVz58yNd1zpFvaXAbpyPc0aAjk3EALw_wcB