It won’t harm them at all. They will be able to walk and talk. I think toddlers with maxed skills might start grade school at a slightly higher grade level than ones that don’t. But that’s super easy to overcome once they start school.
If you have Parenthood installed, that’s the pack that will really impact your kids later because based on how they’re raised it will affect their interactions with other sims once they’re grown as well as job and uni performance. Relax and have fun experimenting with both packs. Just like real life, maybe not all of your sims turn out to be perfect people.
