From a long time ago, I'm a Clarks fitter
Different styles of Clarks shoes are made on different lasts (the moulds that they build the shoes on). It means that one style may fit, when the same size shoe in a different style doesn't. Saying that though, Darcie has chunky feet. They aren't particularly wide (F-G) but she has a high instep and is just big. I have never found a Clarks shoe that has fit her well and now don't even bother taking her there. Start-rite are usually around £4 more expensive but they are a really good fit on her. They just seem to be more generous in width and depth. (Lula, who has skinny feet, is always better in Clarks). Even their canvas shoes fitted her well. We used to get them from Charles Clinkard in the T centre though,
sorry!
As a rule, you'll find cheaper, more "fashiony" shoes are slightly narrower and it's harder to find ones that fit wide feet. We have got lots of crocs though and find they fit well. Or how about finding some kids Birkenstock-like sandals, with loads of adjustability? Hope you get sorted.