I wouldn't worry about it too much...most people I know wouldn't mind the e-mail.
Culturally speaking, this differs from East-Coast to West-Coast, even between the South and Midwest...I know here in Texas that is just being "neighborly". Where I attended my UG in the Midwest they might see it as slightly odd, but won't hold it against you.
Honestly, if that is the worst cultural faux pas that you commit you'll have little to no problems.
Good luck!