Consider letting your kids keep a nature collection.

If it's dead, if it won't rot, if it will fit in the box and most importantly, if Norah agrees to take it straight to the box when we get home, I let her collect it.

This keeps all the boulders, bugs, branches, etc. outside, but gives Norah the opportunity to collect some things, things that won't crawl out of the box, like pine cones and sea shells. And, having them at home gives her a chance to admire their details time and time again.