Is it okay to put all the wallet data to CD? No issues with that in the future? As far as i understand, are there no private keys involved with desktop wallets?
Go to your 'user'/appdata/roaming folder and go into each of your coins folders, inside each is a wallet.dat file. This is all you need to backup for each coin. The file has all the info of how many coins you have on it.
Once you have them backed up you can delete and remove everything else.
Whenever you want to spend your coins you can download a new wallet, and replace the new wallet.dat with your backup copy in the appdata/roaming/whatevercoin folder, but renaming it back to wallet.dat.
Like I said before, when backing up many files, rename each wallet.dat to 'whatevercoin'.dat so you know which is which.
e.g Bitcoin.dat litecoin.dat namecoin.dat etc
If you want to copy them to a CD it is fine.
You can encrypt them with RSA and put it into Datacoin blockchain, after it write down (even on paper!) your private key and transaction number. that's it! you can look into main DTC thread for more info.