iTunes Consolidation from Multiple Sources

I recently got a new laptop and want to take my music libraries from my old laptop and my soon to be decomissioned desktop onto the new laptop. Both are a mixutre of CD’s I ripped and downloaded iTunes recordings. What is the best way to do this. I also have a nano and a shuffle that have the same info, is there a way to upload the data from them? Do I need to de-authorize the old PC’s?