I tried to post this on Tapatalk yesterday, but apparently it didn't go through.
Why don't you add the whole beans directly to the fermenter. You will extract the coffee flavor but very little, if any, of the caffeine. I do this all the time for my coffee porter and it works well. Three days on the beans would be a good start but let your pallate be your guide. I have gone as long as 5 days but to me that might be pushing it a bit. This will save you a step.