isnt the kamek outside of yoshi's island lore refered to as magikoopa? if that's the case, kamek should def be a yoshi's island rep.
Kamek is the character's name while "Magikoopa" is pretty much a term meaning "Koopa Wizard". So, more of an occupation/race description. There are lots of magikoopas in the Mario universe, but only one Kamek.
Kamek himself was definitely the one in New Super Mario Bros. Wii and Super Mario Galaxy... basically, if a generic-looking koopa wizard ever does something
important, it's Kamek (even if his name isn't specifically stated in-game).
Honestly, I actually would consider him as a Mario character instead of a "yoshi" character, simply because "yoshi" isn't actually that expansive of a franchise and Kamek's appeared in a lot more Mario and Mario Party games than Yoshi games.
Edit: The OP is looking great, by the way!