I have this sneaking suspicion that the monarchy is going to skip Charles or that he'll abdicate in favor of William. Divorced and remarried to a Catholic? I don't think even the 21st century is ready for that.
Or a widower and a widow. I think since both have been predeceased by their spouses the divorce is not an issue.
Secondly Camilla is not catholic (except in the very broad sense that the CoE is the successor of the catholic church in England).