Some kids will have different sleep needs. Your son may just be an early riser. My son has started so that, but when I really stop to think about it, is it really bad to "not sleep in" on the weekend? For us, the only day for that is really saturday because we're up early for church on sunday. So maybe trying to get him to change one day out of 7 isn't worth it, it could be harder on him in the long run. If you're being consistent with his bed times/naps then he'll get the rest he needs.
As for sleepy heads. I remember my grandma always had a cold, wet washcloth that if we didn't get up by the 3rd time she'd come wash our face. Let me say we could feel it coming. And sometimes, people any age may need that little "shock" to their system. warmth promotes relaxing, sleepiness. ever notice how if you're snuggled into warm blankets you start yawning? A friend of mine, would run ice cubes down the bottoms of her sons feet to get him up. Even if she gets mad and tries to resist, have a good time with it. if she hears you laughing and having a good time it'll be harder for her to stay mad about it.