Braving the 100 babies Challenge [Support group started]

I think...after taking a step way and playing with just one infant in my family save all the way through I figured out a plausible balance. I noticed that infants have certain grey milestones they have to unlock, in each category. After the primary ones are unlocked the rest are sort of just extra. I am wondering if you should aim to do all the primary ones, in each category. Then when no one grey ones appear you are good. I know when I just focused on one there had to be like 20ish milestones I unlocked without really grinding it. There seems to be 4 standard or expected for each category, minus first, which I do not include because why cute are just to situational.