Luckily the base thinking skills transfer over, so learning how to program in Java/C means that the student now knows how to program irregardless of the language. Picking up a new language is less like learning a new dialect and more like learning the local slang and customs.
Picking up a new paradigm is also harder than picking up a different language within a paradigm you know. But you'll get pretty far with the imperative languages you mentioned.
Except for MUMPS. Fuck that shit.