You can add the worms any time as long as you are not worried about any pathogens from the compost or worm bins.
I've got some worms on order so I went back to read this again - didn't get all the way through it in one sitting.
Question: With respect to coffee grounds in a worm bin, is there such a thing as too many grounds? I'm thinking about the free grounds from coffee shops but don't want to OD the worms on grounds if such a thing can be done.
As long as you have bedding and other food in the mix you are probably ok. I would not go putting worms into a bin with nothing but coffee grounds. Heck, if all you have is coffee grounds, you might be better off simply spreading those around the garden and skip composting them.