Do we sign up for the on-campus abacus class just because half of class 2 did?

School sent home a flyer last week for an abacus programme after school hours, on campus, twice a week. By Monday the class group had half the parents asking about the uniform for it. My son is 7 and enjoys maths as it is. He counts everything, does sums in the car, explains them to his dida on Thursdays, asks me to give him 'hard ones'. I'm not convinced he needs a method on top of that at this age, my partner and I are both a bit wary of starting something because everyone else did. The only real advantage for us is that it's on campus. Weekday pickups are hard for us to manage, so anything that doesn't need an extra drive is tempting. Has anyone done abacus at 7 and felt it helped, or stopped and not missed it?