Not sure about middle names. Maybe sticking with the same theme they could be
Morgan Isolde and
Arthur Tristan.
Merlin is a guilty pleasure -
Merlin Cai.
Peredur might become a new guilty pleasure :)
Kay on a boy these days would be awkward with this spelling. And some of the others might have difficulty with pronunciation. I don't find Igerna/Igraine particularly feminine. And the older forms of
Isolde are not pretty.
Mordred and its variants are likewise very unattractive.
Gawain is also far nicer than
Walganus (quite hideous!). The rest are ok.