It all depends on how you market your books and build your brand "name." There are many authors who are famous for their adult work who went on to market a teen/children's line, that is understood through marketing to have the same talent as their older work, just more tame, or on tamer subjects. (i.e., Frank Peretti, Neil Gaiman) Other authors go the other way around (Suzanne Collins). Either way, the author uses their existing fame to market the fact that they are branching into something new.
Other authors choice to use a penname and market the two separately. As a publisher, I would only recommend this if there is a marketing reason to think that adding another line of books would undermine the sales of either. To use a hardcore example, if you originally wrote nonfiction books supporting atheism, and then want to go write Christian romance, you should probably use a penname. Extreme example, I know
, but in a case like that, the nature of one book would make your stance on the other questionable. Whereas simply writing "safer" books for kids general does not raise any questions about one's character.
If you don't have a highly-established brand name, I wouldn't risk dividing your audience so early if it's not absolutely necessary.
