It does sound prudent to report the seizures to VAERS. Maybe also tell the pharmacist where he got the vaccine?

I got my last one at Walgreen, which was inundated with extra patients because Rite Aid had gone bankrupt. The place seemed very disorganized, the automated appointment booking system had crashed, and the tech was confused about which vax we wanted. All worked out fine, but I was tempted to tell them I would come back when they were less busy.