Try to think about it this way, the valve job is more about the head, the cams\valvetrain have more to do with the ports.
I'm looking at that and I know it's not exactly right, I'm trying to make more of a general point so he can understand what's going on.
The valve job makes the head as a whole function better, whether you have a stock head, or a fully modified one. This is provided it's done properly, of course. Something like the BC4s won't realize their full-potential with port work and other accompanying machine work to either the head or sometimes the whole engine.
The engine is assembled in the factory with parts and machining that all assumes it's working with a specific roster of items. You're trying to change the parts and machining of a stock block and head, so one of the most advantageous things you can do in the interest of your wallet is to have the engine assembled ONCE and the work done ONCE with ONE set of parts. The engine will be the most well-configured it can be if all the parts are present first, all of the machining and balancing work is done with those specific parts, and the engine is completed and ready to be driven.
You can do this stuff as you go, but there is a lot of labor time in doing it that way. Beyond that, the more any given shop, speed or machine, does at once, the more of a deal your generally going to get because the job is easier on them too.
Maybe build an engine on the side and not drive on the same engine\car your trying to build and just do it once? You stand only to save yourself time, money and headache.