What in the hell is wrong with cleaning normal Half Dollars and English Pennys? You're right that cleaning coins is not reccomended for collectible coins that you are collecting and/or selling because it could harm their value.
Of course I wouldn't clean the gimmick, but there is
NOTHING wrong with cleaning normal, ungimmicked coins if they are not collectibles (see, I can write in big annoying letters too

). And normal half dollars and english pennies are not collectibles and are not worth anything more than their legal value (50 cents and 1 old penny sterling). Well, unless they're old or rare, but the ones you get with Digital Dissolve are not old or rare. So clean away!
That being said, cleaning coins with metal cleaner is generally not recommended, but I'm not sure why. Toothpaste works fine for me, but if you're really CRAZY about not causing any damage to your normal everyday half dollar and english penny, follow the steps
here.