Today I searched online for some scavenger hunt ideas and found a great example of one at http://mykidsmake.com/ I typed a similar copy up for us and printed them off and laminated them. I only laminated them because I am intending to use them with my Pippins/Guides, otherwise I am not sure I would have bothered.
I then handed one each to the girls along with a plastic bag and sent them on their way. They were quite surprised but very enthusiastic.
We live on a small lifestyle block so there are plenty of spots to find natural things, although I did actually hide a couple of pine cones amongst some bushes for them to find though as we had none on the property.
It was a great way to spend today's biology class.