Treat him like a new student pilot and it should go well.

I had a couple BFRs that were with pilots who hadn't flown in 10+ years. In both cases the biggest problems were the regs and the coms because so much has changed. The technology has changed a bunch too. Flying was kind of like riding a bicycle.

In all, both students were very receptive. We spent a lot of time working on regs. In both cases the time spent on the ground was nearly three times that of air work. Remember, even though it is your father, it's your certificate.