The great thing with Activators is you get the Alembic low-pass filter, so you get a wider range of sounds than a regular passive P-Bass pickup. They may require some routing, since you have to fit a battery in there.
I have a set in my early-'70s Telecaster Bass -
here's a thread about it.
This track is referenced in the thread - I have flats on the bass but with the filter all the way open it still sounds pretty bright:
8B4X4 Here's another track, this one is played with pick, I adjust the filter gradually through the track so it starts with some bark, but gets rounder as the track goes on:
ostronato If your son's bass sounds good, then I don't think you should get caught up in modding it, but if you do decide to go with Activators then I don't think you'll be disappointed! I actually bought a P-J set for my recently purchased P-bass...