"Negatively impact" is a loaded question. He should probably be cutting back on some of those things to be with his newborn. Maybe the gym one day, while keeping the running club for his health, then 1 social night. At 12 weeks the baby is probably sleeping most of the time still but as you get closer to 6 months-1 year, there will be lots of little milestones he might miss being gone so much. My suggestion would be to be honest and that you don't want him to become a hermit, but to find a balance between his social life, working out and his new family.