Yeah, from what I understand, submitting non-fic versus fic might as well be like working in two different industries.
The one thing you do have to prepare yourself for and I tell you this way ahead of time so that it won't catch you by surprise, is that if she submits to true children's publishing houses (which, since Sam seems to be geared at MG, would seem the likely assumption) be prepared for the publishing process, once it's accepted to potentially take a LONG time. For whatever reason, children's publishing houses move at the speed of molasses in winter. Just as a side-by-side comparison, I sold Adiós to MTV Books, which is a young adult imprint within an adult imprint (Pocket) of a corporate publisher (Simon & Schuster). As such, I worked at a pace typical of most commercial adult houses: I sold in July of '05 on proposal, contract was finalized in late August, first draft turned in by mid-October. I did one major revision that was due in late December. After that, it was easy peasy: copy edits then galley proofs, and the book was published on July 4, 2006, literally a year to the day after I wrote the initial proposal. The timeline for Accent was similar, about a year overall.
Then, I sold Carmen the first time to Dial Books for Children-- so a strictly children's/YA imprint which is part of a larger corporation (Penguin Putnam). I also sold on proposal (in April of '07) turned in a finished first draft by early September, and then started the process of revisions. I was shocked when I was told right off the bat that in all likelihood, the book wouldn't be released until Spring of '09 at the EARLIEST. And that was only if a slot somehow opened up. More likely was late summer/early fall or spring 10. I was utterly thrown, but found out quickly, this is very, very common for children's publishing. Anyone I know who's sold to a house that does exclusively children's books has had no less than an eighteen month wait between sale and publication and more commonly, close to two years.
Again, I'm not telling you this to freak you, but to hopefully keep you from freaking out when Sam sells. I have NO idea why children's publishing works on such a different schedule from adult publishing, but it does seem to be very common. Children's houses also seem to be very in love with revising over and over again-- it really is a totally different mindset and one I'm not terribly well-suited for because while I like revisions (a lot, actually) I also think there's such a thing as too much. I also don't like editing by committee, which seems to be what happens in the children's houses.
I actually told my agent when we submitted Carmen this time around that if it came down to the choice between an adult house that had a YA imprint versus a children's house, that it would have to be a RIDICULOUS deal for me to choose a children's house over an adult house. Which is why I'm SO freakin' happy I'm at St. Martin's.