Why not just create a split WinRAR archive with a strong password and do the same with the USB keys? Seems an awful lot easier to me than messing with TrueCrypt.
That would work just fine also - how the wallet is encrypted and split is a matter of personal preference. However, the hidden volume option with TrueCrypt is interesting - allows you to essentially have 2 different passwords, one would only allow access to a decoy wallet, with a tiny amount of BTC and no way to prove the hidden volume (with the real savings wallet) even exists.
Except that the hidden volume isn't actually hidden.