This is a brilliant movie! Mature 12 year olds can handle it. The only reason I rated it as iffy for 13 and younger was for its violence and sex, which I will mention later. Otherwise, it was an amazing movie. The historical facts are mostly correct. The settings are extremely detailed and large, indeed, awe-inspiring. The acting superb, especially from Cate Blanchett who (as another reviewer mentioned) seemed to be living out the experience of Elizabeth. The facial acting was amazing. The plot was interesting and engaging, if a bit over dramatic at times. Character development was limited, understandably, to the major characters. That should not be much of a complaint, though. The violence was intense - lots of blood and killing, though the battles are not shown until a camera sweeps over the bloody corpses. Depending on your kids you may or may not want to let the see that. In general 12+ have the stomach for it. If they've seen many war movies they should be okay with this. The other concern is that there are two graphic sex scenes. The first you here lots of noise until they're seen through a window and door. They are clothed. The other is with both characters naked, and you can see the full back of the man and the legs of the woman. The camera slides close beside the two, deliberately showing the woman's breast and nipple. There is another scene in which the woman is topless aside from a see-through shirt.
But otherwise it's great. Though there are heads on spikes and people burning at the stake and lots of blood and poison and slit throats. I know . . . it sounds bad but consider watching it.