Free Radical Design (now known as Crytek UK) has not developed anything for Wii. This is the list of games:
*TimeSplitters (PS2)
*TimeSplitters 2 (GCN, XBX, PS2)
*Second Sight (GCN, XBX, PS2, PC)
*TimeSplitters: Future Perfect (GCN, XBX, PS2)
*Haze (PS3)
And no, Diddy Kong is part of the Donkey Kong IP. Microsoft does not have any ownership of it (technically Rare has no property anymore, Microsoft got all of their property when they bought them. Microsoft could shut Rare down right now if they wanted to). All characters created in the Donkey Kong games Rare developed are considered part of the Donkey Kong universe and are owned by Nintendo (before you mention Banjo and Conker being in Diddy Kong Racing, both already existed before that).