Whenever possible install a utility sink in the island to create a fully functional food-preparation area.
Undergoing a kitchen renovation will usually prevent you from being able to use the kitchen. You will have to make alternative arrangements for dinner and plan on living around a mess for a while.
Set the budget and add 10 % for unexpected expenses. If you absolutely need to, you can alter the budget later but this will provide you with a good guide line.
Leaving one wall open without cupboards makes the room interesting and inviting. It is monotonous to have a wall-to-wall and floor-to-ceiling room full of cabinets.