But I think Anakin should have been from Tatooine. Owen's a farmer, and by the way he talked about the Jedi, I just assumed that's the way it had always been. I don't think he would have been out on Naboo flying around with Anakin. Because no one would want to move to Tatooine to start up a moisture farm. Unless of course he was just doing it to hide Luke's identity. But if he had done all that for Luke, I think he would have been a little friendlier to the kid.
So, I have to assume that Owen's from Tatooine and, being that they're about the same age, he must have been really good friends with Anakin. Anakin must have done something important, like save Owen's life, so that when Obi-Wan comes to him with Anakin's son, he agrees to take him in. And, if he's done something big, he must have done it with Obi-Wan around, or he'd never think to bring Luke to him in the first place.
But, then that contradicts Obi-Wan's statement in ROTJ. Anakin can't be the best pilot in the galaxy when he met him, because he's just a little kid (already excluding the pod racing because a kid shouldn't be driving one of those and even if he can, it doesn't make him the best pilot in the galaxy). What could he do on Tatooine that makes him a great pilot? What could he do to impress Obi-Wan so much that he's convinced that Anakin is the galaxy's greatest pilot? Honestly, I don't care. So, for this, I'd be fine with them screwing over the OT. And it's only ROTJ, so it's not that big of a deal.
As for Yoda, I think they shouldn't have shown him at all. They should have just mentioned that he's their most powerful Jedi every once and awhile throughout the PT. Have him live off world, on some planet with no other sentinent beings. If he's that powerful and old, he probably doesn't care about sitting around discussion trade route politics. And that way, by the time you get to ESB, it's an even bigger surprise when you find out who the Jedi's most powerful Jedi is. Oh, and have someone mention that Yoda's dying. That way, Vader has no reason to hunt him down (even though he goes to hide on Dagobah, just in case). So, you assume he's dead by the time the OT comes around. But then you see him in ESB and by ROTJ you find out he's prolonged his life using the Force. But after twenty something years, he can't extend it any further.
As for Anakin's age at the begining of the PT... If he's the main character, he should be in his twenties. But I still say Obi-Wan should be the main character. And there needs to be a big chunk of time spent training in there. In the OT, they're desperate. At the height of their power, I'd think they would spend a lot more time training them and teaching them their philosophy. You could make it so that he's already in the Order and has already had years of training, but I kind of liked seeing how he joined them. I could really go either way, though. My only problem with him in TPM was that he was just an annoying little brat. Had they taken that out and hadn't had him following the main characters around throughout the rest of the movie, I would have been fine with him.