Marine Corps sends their MP candidates to the Army MP school. You're gonna get the same training in the Corps that the Army gets. The Air Force and Marine Corps are two different worlds. When I was in the Marines (EAS'd in '97) the Air Force was referred to as a uniformed corporate job.
You'll have better living conditions in the Air Force which will be better for your family life. The Marines normally live in the crappiest conditions. Pray to God you and your family don't get stationed in 29 Palms. The Army deserted that thing long ago as it was "unfit to live in." That's when the Marines moved in.
Study and re-take the ASVAB. THEN see what options you have. With the Marines, you will have pride like no other branch can give you. The AF option might possibly be better for your family, though.
Of every one hundred men, ten should not even be here. Eighty are nothing but targets. Nine are real fighters, and we are lucky to have them, for they make the battle. Ah, but the One... One of them is a Warrior... He will bring the others back.
"Wrong door, buddy!"
Let no man's ghost say my training failed him.