Okay.. this is one of the coolest things I've heard about in a while! If you head over to Amazon, (or I've heard Toys R Us as well) you can purchase a kit to hatch butterflies! They will send you everything you need, including 3-5 painted butterfly larvae and a netted cage for 15 bucks. The whole process takes about three weeks: you and your kids can observe your larvae turn into caterpillars, then eventually to butterflies. Then you release them off into the wild. Wouldn't that be fun?!
Also, I noticed that Insect Lore has only the live larvae for sale at $14.99 for next year, as you'll already own the net. Right now, Amazon is a little more expensive.