So, here's one activity we've used while running with the kids in the stroller. Grab a crayon and print out a copy for each kid. Just click on the above picture or paste http://www.tekfamily.org/jenmisc/BurkeLakeBingo.pdf into your web browser.
You can't change this PDF, but I just use Microsoft Word clip art to make different versions depending on the season or what types of things you see along your run. Have fun!