I didn't take into any considerations for terrain. Yes, I really should have consider it, but I (my brain) didn't want to worry about dealing with it. Sorry.
However, none of the hills, scrub hills, or scrub plains would count as difficult terrain. (I think.) The jagged mountainous areas do count as difficult terrain. The two undead that ran towards the PCs didn't start out in mountainous terrain.
So, unless the undead or the PCs enter the mountainous areas, there aren't any movement penalties.
EDIT: Sigh... I guess the scrublands should count as difficult terrain. But, I'd rather not worry about it.