Boulder’s Fall Fest. Now in its 25th year, Downtown Boulder’s FREE Fall Fest has become one of Boulder’s most beloved community celebrations. This 3-day autumn festival September 21-23, 2012 features food, brews and music with the added excitement of a Children’s Carnival and more than 30 artisan booths. Friday: 5 p.m., Saturday & Sunday: 11 a.m., Pearl Street Mall, 1420 Pearl Street, Boulder. http://www.boulderdowntown.com/events/fall-festival

Hop, Skip & a Jump Start. Lace up! On September 23, the Children’s Museum of Denver will hold Hop, Skip & a Jump Start–the perfect race for every member of the family. With a stroller-friendly 5K, an Infant Crawl, Toddler Trot, Kid Course, and a day of activities and healthy snacks, it’s the perfect way to teach a healthy lifestyle. Prizes awarded. Tickets are $10+. Call 303-561-0104 for more information or go to their website http://www.mychildsmuseum.org/.

Touch a Truck. Have a little one who loves heavy machinery? On Saturday, September 22 from 10 a.m.-1 p.m. they can climb aboard monster trucks, emergency vehicles and a Zamboni. Participating agencies include the LIttleton Fire Department, City of Centennial, City of Litleton and South Suburban Parks and Recreation. Cost is FREE! South Suburban Ice Arena, 6580 South Vine Street, Centennial. sspr.org.

Nemo in 3D. That natural aquarium the sea seems created for 3D — those colors, those fantastical inhabitants, those sharks (my, what a toothy grin you have). And Disney/Pixar are taking advantage of advances in technology to send a beloved clown fish named Nemo and his fretting dad, Marlin, on their separate journeys from the Great Barrier Reef to Sydney, Australia, in “Finding Nemo 3D.” Check your local listings.

Thomas the Tank Engine puzzles many adults but inspires maniacal devotion in the hearts of children of a certain age. The character, which launched in print in 1945, has been successfully adapted for a number of TV shows and toys around the world. Now Thomas is coming to life — all 15 tons of him — at the Colorado Railroad Museum as the Day Out With Thomas: Mystery On The Rails Tour 2012 stops by Sept. 22-23. Little engineers and their families can ride with a Thomas replica and enjoy Thomas-themed activities, including storytelling, magic shows, live music, arts and crafts, and more. 8 a.m.-5:30 p.m. 17155 W. 44th Ave. in Golden. $18. 866-468-7630 or ticketweb.com.

Children’s Consignment Sale. The Just Between Friends of Denver consignment sale is the biggest of the big and will be held September 20-23 at the National Western Complex in Denver. Thursday 10 a.m.-7 p.m. $3 admission, Friday 10 a.m.-5 p.m. $2 admission; Saturday: 10 a.m.-3 p.m. (25% off sale) $2 admission and Sunday 9 a.m.-3 p.m. (Half-price sale). jbfsale.com/denver