well if it's going to be summertime....
as a boulder-ite i LOVE the farmer's market. go pick up some fresh fruit and such. perfect snack for a hot summer day!
and as far as activities....i'm not real familiar with bridal showers, but how about something crafty if it's appropriate? maybe everyone makes a patch (stencil/sew/draw/etc) for a quilt that you could throw together for the happy couple? maybe decorate vases that could be could be centerpieces for the wedding? maybe a scavenger hunt hike?
wild flowers would be a great decoration...just make sure no tree huggers see you picking 'em!
and of course, anything should also involve dogs and recycling and organic hippy fun! ha!