I would highly recommend choosing a computer and ordering it online before your son gets to campus. There is so much going on at the beginning of freshman year that it's not wise to have to worry about finding and setting up a computer at the same time.
Case has very nice discounts and deals set up with Dell and Apple - the link is:
http://www.case.edu/its/estore/computer.htm . Your son will need to log in with his Case ID and password (same as the login information for email). Most of the humanities and lower level science classes don't require much from a computer - basic word processing and stats software is probably all he'll encounter.
I can't make a recommendation for desktop vs. laptop. There are plenty of computer labs around campus, and many students don't bring their laptops with them, but I have enjoyed having the flexibility of a laptop.