DIRECTIONS:  From Denver, take Lowell Blvd north to 69th Place and make a left (west).  Follow 69th as it becomes Osceloa Street and heads north.  You'll see the large parking area for the testing grounds.  You can park here, but you may be better off parking along the street just past the testing grounds, just in case people need to...you know...test things...
The Little Dry Creek Trail is a multiple use paved recreation path that cuts through Westminster and Arvada.  The segment between Federal Blvd and Raleigh Street is interesting because it traverses Westminster Station Park.  This park was built around a new light-rail station and was magnificently thought out.  

While you can park at Westminster Station Park, I recommend starting near England Park and the testing grounds tower, just to the west.  Starting here gives you a little longer of a hike and explores more of the Little Dry Creek Trail.  As you enter the park you'll immediately notice the various bridges, ponds, and water features that make this park so interesting.  From the higher spots in the park, mostly the bridges, you get nice views to the west of the Boulder Flatirons with the Indian Peaks and Rocky Mountain National Park peaks in the distance.

If you want to continue exploring the Little Dry Creek Trail, the trail continues to the east by following the light rail line under Federal Blvd.  After half a mile, the Little Dry Creek Trail connects with the Clear Creek Trail.  Westminster Station Park is a great park to bring your kids to as they will enjoy playing on the concrete structures and jumping across the various creek crossings.