^You make her older than you have to also make Anakin older because otherwise: eww. I mean not that there's currently a shortage of "eww" as things stand, but that would sort of put it over the top.
I'm not sure exactly why Anakin had to be found so young, after all Luke didn't start training until he was in his late teens/early 20's so the "too old" bit seems a little disingenuous. Maybe it was to make the attachment to the mother stronger and by extension the loss that much greater?
The primary driver, from what I understand, was the idea that there would not be the anxiety of separation between Anakin and his mom, and thinking he wouldn't be all that upset if he were older. While I get that point, I personally think that Anakin should have been older, and that their relationship could have been built up in a different way.
Regardless, I do think the ages were a minor problem, but the overall political scheme is one that I think needed a little more polish. Palpatine and his machinations are great, and I enjoy some of the Senate scenes. But, in the larger view, they don't make as much sense.
Part of this is owed to Padme's subplot being largely excised from ROTS and leaving much of the skeleton work of the Empire's formation unseen, which would go a long way for expounding upon Tarkin's remarks in Episode IV, which is what a prequel should do.
Padme's sub-plot before the reediting involved only one scene, but after Anakin's fall was reshot they actually expanded her role in the movie, making her the focus of his reasoning for joining hte dark side.