I think you are in for a treat with this science project, but let me warn you, it might take a little research to get what you want. I can't at this moment write a long answer to your question, but I am going to suggest that you read the WHOLE thread of questions and answers at the following website

here

I am pretty sure you will find enough information to go on with your project. Good luck!

Since I am not intimately familiar with your set up I will answer the question as best I can.

I found a simple procedure on the Internet that utilizes a 9-volt battery and items you can purchase at your local drug store. With this procedure you can plate pennies with zinc, bismuth, and mercury. But you can also use the solution you already have of silver nitrate in order to plate silver on the penny.

Here is what you do:
1. Fold a paper towel up into a 1"x 1" square. Fold aluminum into a 0.5 inch square with the thickness of a penny.
2. Put four drops of calamine lotion in a small beaker. Add some vinegar to the solution. I am not certain what the optimal amount of vinegar is so you should test it out with 4 drops first and then increase the amount of vinegar you add to the solution in order to get the best result. Stir the mixture and pour it on to one end of the folded paper towel.
3. Make approximately 25 mL of a saturated sodium chloride solution. Pour this solution on the other end of the paper towel. The salt solution should be touching the calamine portion of the paper towel.
4. Place a clean penny on the calamine portion of the paper towel and place the aluminum foil on the paper near the penny. Invert the 9-volt battery and place the large terminal on the penny and the smaller terminal on the aluminum foil. You will probably need to secure the battery with a long piece of electrical tape. Leave the battery on the set up for approximately 5 minutes.
5. Remove the battery from the set up and dry the penny. It should be coated with zinc.
6. You can repeat this procedure using different paper towels, metals, and solutions. There is a list below.

Replace the Calamine and vinegar solution with Pepto Bismol. This will coat the penny with bismuth.
Replace the Calamine and vinegar solution with Mercurochrome stain. This will coat the penny with mercury. Warning: Mercury can cause heavy metal poisoning. Wear gloves at all times while handling the Mercuroshrome stain. Only use a small amount of the stain. Be sure to read the label of the stain before use.