Koby

The train leaves from terminal 2 only. And the metro does not go anywhere in town where most visitors want to go. But in some cases, especially if budget is important, they do the job.
But my understanding is that aster wants to make this as simple as possible for the inlaws...?

If they can manage to walk over to the taxi rank and get a taxi there, there is nothing wrong with that. Waiting times are short, and there are only official taxis there (but what kind of car - and driver - you get is a bit of a lottery).
But I'll send you a link to the taxi company that I have been using for 20 years or so. I norrmally just call them after arrival (and they then show up within 5 minutes or so), but for an extra fee they can wait for your inlaws after customs.