http://www.montgomeryparks.org/brookside/documents/bgmap_color.pdf
Right next to the huge playground and picnic areas of Wheaton Regional Park, these gardens are simply gorgeous—any season of the year. With a wide trail perfect for little guys’ scooters or bikes with training wheels, the path is mostly flat with great spots to stop for a picnic. In our crazy life, we really enjoy the serenity of walking through a perfectly manicured garden with flowers a bloom everywhere. And my kids love to try to find frogs in the fountains. If there are no frogs to be seen, any of the kind gardeners are usually up for helping the kids hunt one down.
I can't rave enough about all the programs this place offers. There are programs for adults as well as kids (http://www.montgomeryparks.org/brookside/childrens_programs.shtm). Most are free. Admission to the gardens is free (its a public garden) but some exhibits and programs have a fee. They have an uber cute kids play area with garden play area (think dirt instead of sand), a real treehouse (which I want in my own backyard), fairy houses, and building table. In the early fall we dressed the kids as fairies and my photographer friend took pics. It was the perfect backdrop!
Right now in the summer they have an amazing Butterfly Garden open until Sept 20th which costs $6 per adult and $4 kids 3-12. Which is definately worth the price! A few warnings...butterflies need a hot environment so expect to sweat, sometimes the exhibit closes due to extreme heat call this number before going "Wings of Fancy" Hotline: 301-962-1453, and no strollers allowed inside (bummer).(http://www.montgomeryparks.org/brookside/wings_of_fancy.shtm)
In the winter, they have an amazing light display called "Garden of Lights" that you walk through...but be forewarned lots of people will alway want to attend so either get there before dark or expect to wait in a long car line waiting to park (though they do have an efficient parking system). Hours are from 5:30-9 (last car admitted at 8:30pm. It costs $15 to park on weeknights and $20 on weekends...but again worth it!http://www.montgomeryparks.org/brookside/garden_lights.shtm
Have fun!