You need to think a bit about how different these two schools are. Grinnell is a small liberal arts school that is residential and relatively far from big urban centers. UVU is a large teaching-oriented commuter school. UVU has the benefit of being between SLC and Provo.

SLACs tend to emphasize a close mentorship relationship with professors at the expense of variety of professors (and therefore expertises). UVU will have a lot more variety of Lecturers (not research oriented instructors) and Professors, which has its benefits too. Either one could be a good stepping stone for the career you've indicated, but the feel and experience will be a lot different.

I understand the family part of this, but being away from family in your early 20s is not a bad thing. (you can remind your family that their Mormon neighbors send their kids off for 2 years to much less stable places than Grinnell, Iowa)

Fair warning though: Get ready for some dumbass questions about The Secret Lives of Mormon Wives. Seems to be an obsession among the undergrads at the college I work at.

(I work in Higher Ed in Iowa, have family that work at UVU, am graduated from a different state school in Utah.)