I'd like to see Apple produce an aggregator that will edit an epub for $5.00 and not charge a percentage of sales. That's a laughable claim.
If your children's books are a) fixed-format, image-only (so, for example, you had a bunch of jpegs and put them one after another in an epub), Apple will reject it; b) if you have the WORD Kindle or Nook in your book, Apple will reject it; c) if you have a bookcredit line, or a link to a publisher or your own author page, Apple will reject it...OR, here's my favorite: if Apple just does not think your book is "good enough," or high-quality enough for its iBookstore--in other words, they just don't LIKE it, they'll reject it, time after time after time, until they wear you down. I'm not saying that's what is going on with you; but I have a client who persists in doing his own cover design, and at the end of the day, the books look crappy. Apple came up with a *list* of ridiculous excuses, and I didn't have the heart to tell him that his book is just not good enough-LOOKING, that his table images weren't "cool" enough and his cover just didn't cut it in Apple's iBookstore...so I told him to blow off the Aggregator (who was getting $50/pop intake fee plus 5% of sales) and just sell his epubs on Nook and Goog.
I realize that with kids' books it's a whole other thing...but I have stopped taking children's books precisely because they aren't selling well enough, even on iBooks, to warrant what I have to charge to make them to Apple's new fixed-layout specifications. I know no childrens' book author wants to hear that...but Apple is such a tiny, tiny, TINY percentage of ebook sales that I don't feel right taking childrens' books authors' money. I can, if you want to PM me, refer you to someone who does do fixed-layout children's books by preference; but I do not know what he charges.