Full month/100 days

of course you can celebrate both. never heard of any taboo of this. But you and baby will end up overtired. I didn't really celebrated for both my boys. only very simple prayers and gift boxes for the elderly to feel happy during the full moon. Personally doesn't like people to keep touching or carrying my babies. 100days doesn't sounds auspicious to me so I skipped it. only gave angpao and blessings to them.