If the laptops really need upgrading then go for that. An ipad2 is great (I'm typing on one now) but for a student who will need to type essays, plug in printers, share files with friends, easily navigate websites etc then an iPad will not come close unless you spend lots on extras such as Bluetooth keyboards, specific printers etc etc
I'm sure they would more prefer a iPad as its much more the thing to have but for me it does not come close for real study assistance.
As I say, depends on their laptop. A 3yr old laptop could probably be upgraded with some cheap RAM and maybe a hard drive. They could have the best of both