Not only correct, in my view, but much better.
It's aros am, and using aros ar gyfer (translating directly from the English) will sound like learner-speak to many people, I think. Unless things have changed radically in the last ten years.
Ar gyfer does mean 'for', of course, but really only in the sense of 'for the benefit of', which is not the sense in things like 'wait for'. So we DO say, quite rightly:
Mae hyn oll ar eich cyfer chi
This is all for you
But we DON'T say:
* Nes i dalu pum punt ar gyfer peint o gwrw yn Llundain
I paid five pounds for a pint of beer in London
(should be: Nes i dalu pum punt am beint o gwrw...)
Maen nhw'n aros ar eich cyfer chi
They're waiting for you
(should be : Maen nhw'n aros amdanoch chi)
where, in both those cases, 'for' does NOT mean 'for the benefit of'.