Well, they are already given a link if they do not have the runtimes. A direct link to the download might be better, however.
That being said, if they can't figure out how to do that themselves when given a link right to it, are they going to even be able to figure out your game?
I would vote for a direct link, but I dont know if including the runtimes is needed even as an option. That is just me, though.