I dunno, at that point it's almost a character-building name, I think. If you can survive that name you can survive anything. Just the practice you'd get correcting the spelling would probably boost your intellect.
Really once you say them out loud, they're pretty normal. Carrington-McKinley and Kayley-Hunter. I wouldn't have gone with the hyphen personally but probably no one says "Carrington-McKinley, here's your lunch!" on a daily basis. They're Carrie and Kayley, maybe. Or rather, Kharrie and Khayleigh.
Sometimes changing the spelling can add zest to a dull name that has a great sound. Okay, in this case I think they went too far. But for example, Wilhelmina seems very stodgy and old-fashioned to me, whereas... Willamina seems much more modern and romantic. Same sound. I wouldn't begrudge someone changing that spelling. Maybe the Sparks family has a particular affinity for the letters H and Y... ??