I personally would do Warhammer Roleplay, as it sounds like they actually want to roleplay and I don't think D+D is the best system for that, it's far too focused on tabletop munchkinism.

I think Griff's point about licensing is really good if your folks are newbs, it can really help to have some automatic familiarity. That's a place where Warhammer Roleplay may fall down. Depending on edition, it can also be fairly unheroic at times (characters dying, etc).