Unfortunately, unless you want to use the coins as jewelry, cleaning WILL destroy any value. Coin collectors like original condition. If you insist on cleaning them, don't use any abrasives -- not a toothbrush, or even a paper towel. You need to use very, VERY soft cloths, and you should wear cotton gloves when handling them, to keep the oil from your skin off the coins. If you wish to preserve value, then use only a very, very soft cloth merely to dislodge cakes of dirt.
Purchase archival grade storage items -- paper envelopes, or cardboard displays, or plastic cases -- as you prefer for storing and displaying. When you show them off, handle them with the cotton gloves.
And don't discount the coins, unless you're done some research! Individual coins from the last 100 years can be worth a great deal. I myself own an American three-cent nickle that I unearthed in my backyard, which is worth many thousand times more than its face value. The amount of silver in a coin also counts a great deal -- just as melt, an ounce of silver is worth just under $20 as of Friday's market.
