Ken, you may want to look into photoreflect instead of smugmug. it's really designed so you can put thousands of shots up quickly, and their system prompts you to upload ordered hi-res files when they are ordered.
It's worked pretty well for me, and I like how it allows me to easily organize the race shots I take.
http://photo.mohflo.com is my site. It's nothing flashy or pretty, but it seems to get the job done, which is 3 clicks to get to your pictures.
the manual process you described for order flow is automated with the photoreflect software, so you literally get an order notice in your email, fire up their software, hit the 'print order' button, and it handles uploading the originals and sending an email to the client stating their digital download is ready.