How close to the ends of the island are junction boxes? I would generally go big, but want to make sure they’re not too close to the ends.

Here is a guide with measurements

Thank you susie appreciate the diagram

Its 18 inches from each junction box to each end of the island

and its 36 inches between the two junction boxes.

So for the 10” that gives you 18-5= 13 and for the 12” 18-6=12”. I think either would work in that respect. So the junction boxes are 36” apart? That gives you 24” between the larger pendants and 26” for the smaller ones. I tend to like larger pendants myself so I would choose the 12”

Thank you so much for your opinion and help Susie . the way you broke it down really helps. I think i will do the 12 , I also have a matching wall sconce that is 6 inches in diameter going above shelves, so I think having the 6 on the wall and the 12 which is half the size up will look nice .