You know your cats better than anyone. If you say that they won't freak out and it's easier on your mom, you could easily transport them there. My cats would be total freakazoids and everyone would be miserable including the catsitter. We know that cats don't like change much and they probably would be more comfortable and calmer in their own home but you've got your mom to consider, too.

Btw, can you share where you're going for vacation?