[SPOILER]They did take more than two people… at the end, you saw lots and lots of similar spaceships flying off earth, implying they took a substantial number of Earth children with them to start the new society. No matter how sophisticated their technology, it was believable that they couldn’t take everyone or even like 1%, since that would be something like 60 million people. I thought the fact that they didn’t take the parents was kinda off though, and just thrown in so they could have a melodramatic breakup between Nicolas Cage and his son.
To answer Trillian’s question, the whole solar flare thing was an imaginary disaster invented by the screenwriter; whatever happened with the sun in the movie doesn’t exist in real life, so he could make it as powerful and unstoppable as he wanted to. Having cool looking spaceships doesn’t make you omnipotent, either.[/SPOILER]