Worry about it the month before you actually go to school, but I would recommend a good laptop. I don't think the iPad will have decent electronics sim programs and the like by that time. That stuff is handy in labs.
Labs can definitely be an important factor - I know I had to use make use of my USB ports in several of my labs (something the iPad lacks). Also, many universities require laptops that meet a certain criteria - I would also look into that for your school before purchasing one.
That's probably a good recommendation. While getting an iPad and a mac mini could be an interesting option - and you'd have a great opportunity to develop software for it in order to actually make it suit your needs - keep in mind you couldn't do any programming on it.