I went to see this last night, for a laugh, so I thought I'd post a few thoughts on the Classics and heritage-related elements. Warning: spoilers follow.
I thought the first Night at the Museum film was fun, though I became annoyingly obsessed with the fact that the museum obviously isn't a Museum of Natural History, but a general museum devoted to human culture through the ages. This one moved most of the action to the Smithsonian, so that was one problem solved.
OK, let's get the pedantic rant out of the way - HowcomeTeddyRooseveltcanreadhieroglyphicsandwhywouldheusetheword'figure'inatranslation
Other than that, Steve Coogan's unidentifiable Roman is pretty fun (Octavius? Did someone get Octavian/Augustus' names wrong or is he just a random Roman guy?!) and speaks in the traditional BBC British Roman accent (see here). He's very interested in nobility and honour and duty - I'm sure Aeneas would be proud. Hank Azaria's evil Egyptian Pharoah speaks with an upper-class British accent and comedy lisp, which he presumably picked up from British Egyptologists. He asks if Larry speaks French first, which I thought was a nice touch, as presumably it's a nod to the discovery of large amounts of Egyptian artefacts by the French from Napoleon onwards. Napoleon himself was worth a laugh or two, and all his French was accurate. As for the others, I liked Ivan the Terrible insisting that he's actually Ivan the Awesome and I loved seeing Oscar the Grouch on film again, one of my favourite Sesame Street muppets.
Actual historical artefacts are generally only used when they're needed for the plot and the New York museum in particular seems to bear more resemblence to Madame Tussauds than a museum. This impression is reinforced at the end when visitors are allowed in at night to see the exhibits talking about themselves. Its not a bad idea - I'm quite a fan of living museums like the Midlands' Black Country Living Museum - though in a way its a shame that no one gets excited about artefacts that don't bring waxworks to life and open the gate to the underworld any more.
Talking of which, the underworld scene was pretty cool. The bird-headed creatures were presumably inspired by the Egyptian god Horus, who was shown as a falcon or with a falcon's head. He was a god of sky and kingship, but he was also associated with funerary rites and his myths blended with other hawk-gods. I'd have taken the opportunity to have the real spirits of Ameila Earheart etc appear out of the underworld, but I think that would have taken the movie out of its cheesy, light-hearted tone.
Like the first movie, I thought this one was fun and mildly amusing, though hardly a cinema classic. Amelia Earheart's slang-ridden way of speaking kept reminding me of this Monty Python sketch, which affectionately mocks all those World War Two movies I used to watch in the afternoons when I was little. Overall, I wouldn't make a special effort to see it, but if you're bored and fancy a trip to the cinema, its cheerful and entertaining enough to pass a dull evening.