Thanks for the feedback, everyone! I really like the treasure bag idea. We get a lot of mileage out of "I Spy" already, but that reminds me to learn some silly camping songs to teach them en route. Our longest "urban tour" so far has been 19 miles over 6 hours - with plenty of playgrounds, parks, sheltering from a thunderstorm at Dairy Queen, and a movie along the way.

-Glen