You could make that case about ANY family film, whether it be Old Dogs or Up, kids will like anything, so much so that it's only up to parents' discretion on what they want to sit through, unless it's something the kid really wants to see. A lot of parents I know hated "Shrek the Third" a lot, and their kids were more than bored during it. Don't forget that a large part of Shrek's box office factor comes from older viewers who also detested the third film as well. Heck, IIRC, the Cinema Score rating was a C!
You simply can't ignore the fact that Shrek the Third, despite its box office earnings, was not well-liked...