Since
Campbell breaks down to Camp + bell, it comes across as wordy as well as surnamey even if ringing a bell to alert campers has nothing to do with the etymology.
Campbell has less teasing potential than a surname like Cockburn, but Campy might not be great to hear a lot especially if the kid doesn't want to be shoehorned. A boy with the name
Campbell would probably go by
Cam to his friends. Do you like
Cam?
Campbell does stick out as very different from your other two children's names but so does
Macaulay.
Other names you might like:
ArloBrodie CallumConallConnorCalebDesmondDominicEvanderLewis - popular is Scotland
Malcolm MaxwellMilesRoland