In Al Capone Does My Shirts, it says on page 3, "There are 23 other kids who live on the island because their dads work...like my dad does."
In Al Capone Does My Shirts, on page 34 Moose's dad tells him, "'The convicts do the washing here.'"
TO LAUNDRY ROOM
In Al Capone Does My Shirts, on page 207 Moose asks Piper, "...It's your mom who censored the mail, right?"
According the the author's note in Al Capone Does My Shirts, "The families of most of the guards and prison administrators lived on the island." The families of the guards did, in fact, live on the island.
In the Author's Note it stated that, "Capone's first job on Alcatraz was working the mangle in the laundry facility." The statement aboves shows that Al Capone did the laundry at one point, but not during his entire time at Alcatraz.
The Author's Note told me that, "The convict's mail was routinely censored and wives of the guards were occasionally asked to help out with the task." This proves that the wives did not always help with the mail, only occasionally.