It's a diminutive form of "дети" (deti), which means "children".
While it's not used as frequently in modern Russian, you might still hear it in some regions or from older speakers.
Here are some examples:
* "Мои дятки уже спят." (My children are already asleep.)
* "Старые дятки любят рассказывать истории." (Old children love to tell stories.)
However, using "детки" might be considered a bit childish or even patronizing in formal contexts. It's generally best to stick with "дети" in most situations.