I thought you might like this chart showing the qualities of different milking goat breeds. Keep in mind the amount produced is when they are full time milking and not feeding kids. I co-share with the kids when milking. I only milk once a day, after locking the kids away from the doe's overnight, I milk in the morning and then the kids go into the paddock with their mum all day. Bottle feeding kids is a full-time job, and it also produces extra health complications for the kids. Breast is best if it's possible to raise strong healthy kids with excellent rumen function. @Michelle Illig on thinking about it, Nigerian Dwarf would be the best option for you regarding butter, but because goats are herd animals and its best to keep 2, you could maybe have a high milk yielder also to give you the quantity of milk needed for your family.