I would go with Tuck, what I heard and have seen of it looks really good.
Unless they are major musical theater nerds and listen to the cast recordings of the classics already I would stay away from King & I, Fiddler and She Loves Me, as much as I liked the latter. Both Fiddler and King & I are almost 3 hours with a very long Act 1, I liked them but I even found that a bit long to sit through. Seems though for 11-years olds, again, unless they have already developed a love for the classics.
Something Rotten could be a good alternative, but I don't know many many shows they know (from OBCs and such) to get all the references. It's only half the fun if most of those go over your head... and there are lots of inuendos in the show as well, which might be a consideration...
Daddy Long Legs is now one of my favorites musicals, and if you want to take them to a more quiet, intimate show as a contrast to SoR, go with that one over She Loves Me. The themes of that show are much more relatable for kids than She Loves Me, which is a straight-up romance.