Outlets are required in a fixed in place island. Best to check with electrician or inspector about how many. Around here I'd usually be including a minimum of two, some inspectors could require 4.

Currently, you are required to only have one GFI outlet from one of the small appliance circuits. But with a 10' island, it would be a safety hazard to not have outlets somewhere close to both ends. The spirit behind the requirement is so that small appliances don't use extension cords draped everywhere. If you ever want to entertain and use the island as a buffet, it's best to have enough electrical on it to run the warmers, crockpots, and blenders that will be in use. I'd do a quad close to both ends, and maybe even a popup in the middle.

That means you will need a dedicated circuit for your MW, and the GFI protected outlets from part of your 2 required small appliance circuits. Because electrical useage has done nothing but increase, I'd go ahead and have outlets from the second small appliance circuit as well. Or maybe outlets from one of the small appliance circuits plus a run of another island only GFI small appliance circuit. You're trying to use the two (or three) circuits to avoid overloading any one with demands. It's never fun just when the party is starting to have to go and flip a breaker and then try to re-arrange all of the juice suckers to not pop it again.

You should look at the specific applicable codes for whereever you live. In California, one is required if the island is greater than 24"x12". If you have a rangetop or sink on the island, then you need two.

See 210.52.C.2-5 below:

California 2010 Electrical Code