I think it depends on what TYPE of kid lit. YA? I always have adult fic writers read & crit. MG? Nope. PB? Nope. [size=78%](I actually prefer that my adult fic friends who read my YA are not kidlit readers. . . much like I try to get a SFF reader and a romance reader. In series books, I like a reader who is new to the series & so missed the earlier books.) [/size]
I ask them to flag anywhere they were tempted to skim or skip, anywhere they had to stop to think about the plot or character, anywhere they were confused. The rest I suss out post-reading bc leading questions make me fear that they'll go in anticipating an area of weakness in the places I pre-address.
That said, with the middle-grade . . . I rely solely on my kids, a few of their friends, a few moms, & my co-author. No adult fic writers there or really, YA writers unless they're moms who read MG. I have a totally crit different process there.