I would pull 2 brood frames and put in each nuc with nurse bees If they are booming and there is a lot of frames of brood I would put 3 Im assuming this will be a 5 frame nuc. be careful not to take the queen. as a safety net I always make sure there is a frame of eggs in the original hive just in case you miss her.
I would remove a total of 4 frame of sealed brood from the two booming hives and place one of these without the bees into each nuc. a week to 10 days or so later I would look again and consider repeating the process.