Reddit mentions of 2012 Guide Book of United States Coins: Red Book (Official Red Book)

Even paper envelopes aren't a great idea, as paper is often acidic. Any coin store will have inert plastic holders or flips that you could put the better coins into. I wouldn't worry too much about touching the coins, unless any of them are uncirculated; then the oils on your fingertips would tarnish them. Just make sure that they are individually cased so they don't clink together and get scratched. If she's looking up values, then the Yeoman guide would help; it's reasonably priced, and your local library probably has it. Also: DON'T CLEAN THEM.

You can buy this book:

http://www.amazon.com/2012-Guide-United-States-Coins/dp/0794833470/ref=sr_1_1?ie=UTF8&qid=1319846835&sr=8-1

It's called the "Red Book" in the industry. The prices are not entirely accurate, but will give you a rough idea whether a coin is worth $1 or $1,000.

1964 and earlier half dollars, quarters, and dimes are 90% silver, and are currently selling for about 25 times face value. Keep in mind this is just for scrap, common dates, though. If the coins are better condition, or better date, they're worth more.

If you have a few specific coins about which you're curious, I'm happy to look at them.