The National Treasure movies aren't exactly intellectual fare; I'm pretty sure you'll be able to see the second without having seen the first. I mean, you know how the first one goes -- boys meet girl, boys steal Declaration of Independence and spend the entire ridiculous movie on the run from the bad guys and the FBI, boys and girl (and one boy's dad, but that is overcomplicating things and I don't like Ben's dad, anyway) find treasure, cooler boy gets the girl, dorkier boy gets a Ferrari -- so I'm pretty sure the only thing you'd miss are some stupid in-jokes with reference to the first film or something.

I think you should cave. :D