I am new to caching as well, but have found a few already. What I usualy do (I go caching with my kids as well), is go to a Dollar Store, and stock up on whatever I can find that is small that I think someone wouldn't mind finding.
Usually all the caches I have found so far have matchbox cars, Boxes of different types of kids card games, bracelets, stickers, plastics bugs, key chains, small action figures/dolls ect. I did find a "Large" once that was stocked with CD's, Scrapbooking paper, Burnt movies, paper lanterns, ect. Luckly that one was near the road, so I had to run to the car and find something a bit better to put back. But for the most part, don't expect to find any "real" treasures, as everyone knows it is only so long before the "muggles" come and grab it all.