Assuming they are registered voters, just go to the nearest voting location (tell them google it, but it's probably a local school) with a valid I.D. Assuming they are not registered voters, not much they can do now.
As for who they should be voting for, I don't think you should be influencing that decision. Let them make up their minds. If they are in favor of the Dream Act though, voting Democrat is the best thing they can do.
