Fairly sure the constitution doesn't allow for a voluntary skip, the to be Monarch has to actively give it up?
Ah, but that is the interesting point. The British do not have a written constitution codified in one document, but is in the form of thousands of legal papers and decisions basically since the Magna Carta of 1215, which in itself did not become law until 1225. Therefore our laws can be changed relatively easily, especially when compared to the American Constitution, which has only 27 amendments, so it would be
possible in theory for a modern Royal to refuse to be crowned and pass the honour on to their son or daughter, the former in the current case. No doubt new legislation would have to be created for this to happen.
Will that happen, given Charles age, and the stresses of modern kingship? Who knows, but anything is possible!