Hi,
For 10 bantams you could probably do a coop that is 4x6 and 6x10 for the run? I am a fan of having an elevated coop so the chickens can use the space underneath to escape the weather. The total ground space would be 6x10. If you can afford more space, then the better.
This is from the McMurray site: "Bantams, being smaller, don’t need as much space per bird. This is one reason they are popular in backyard flocks. 2 square feet per bird is adequate if they are allowed daytime forage, so a 4′ by 8′ coop could house 16 bantams. We recommend a minimum of 5 square feet per bantam if they are kept confined, so a 5′ by 10′ coop could contain 10 bantams."