I'd probably say their power wouldn't change if he'd birthed them at full power or not. Creating 7 new lifeforms each roughly around maybe 55-60% of Goku's peak at the time (if not slightly more) with far less effort than Piccolo Daimao needed to create Cymbal or Drum does seem a little bit of a stretch to do if purely based on the suppressed Cell who's power is at best equal to 2 Cell Juniors.