This is a work in process but as a father of two little girls, I have a lot of experience in entertaining little minds.
Albany/ Millersburg
Albany Parks and Rec- Albany has some amazing parks, activities, and events. My favorites are the splash pad at Monteith Park, the nature trail at Teloh Calapooia Park (look up Albany Telephone in the Wild), and the play structure at Deerfield Park. The paddle boats are a cool addition to Waverly Lake. The NW Art and Air Festival at Timber Linn Memorial Park is a MUST. The also have activities and classes you can sign up for to entertain and develop your littles skills and confidence (like dance classes). albanyoregon.gov/parks
Albany Vistors Association- The Albany Visitors Association is a great resource for keeping up with happenings in the area. They also have fun activities like Kids Passports where you complete objectives throughout the community. www.albanyvisitors.com/
Albany Historic Carousel & Museum- I've been on a variety of carousels over the past couple years and this one is truly the best. The stories about each animal are unique! I highly recommend taking a tour in the basement of the carousel to learn more and see the carving workshop! albanycarousel.com/
Walk Downtown- The Historic Downtown is a great spot for a walk with great shops, the Carousel, restaurants, a movie theater, and riverfront park with views of the Willamette River. albanydowntown.com/discover/
Linn County Expo- The County Fair is definitely awesome! Throughout the year they have other cool events such as a reptile show, motorsport events, car shows, rodeos, dog shows, and a variety of other happenings. They have a text signup to keep in the loop if you don't want to miss anything! www.linncountyor.gov/fair-expo/page/events
Lakeshore Lanes- bowling, putt putt golf, arcade Lakeshore Lanes
Heritage Mall- shopping, arcade, indoor play area (marked no weapons/ CHL)- www.heritagemall.com/
Jefferson
Greens Bridge Gardens- This is a great spot to visit from U-pick to events. My favorite trip out was picking strawberries with my littles! They have a great Halloween event too. www.facebook.com/greensbridgegardens/
Santiam River- There is one boat launch in Jefferson that you can walk part of the shoreline of the river. Or you can sit in the River View Park and watch the Santiam flow by. An across the street resource is the Riverside Grocery Store where you can pickup snacks, chips, ice cream, or any other picnic essentials you might need.
Matt Withee Memorial Pool- its a great place to cool-off in the summer heat!
Jefferson Chamber of Commerce- The Chamber is involved in a lot of fun activities throughout the year such as Heroes Day (fireman's breakfast, vendors, car show, parade), Pumpkinfest (Halloween-themed event with vendors and fun for the littles), and the Christmas Parade. www.facebook.com/JeffersonAreaChamberofCommerce
Jefferson Public Library has a lot cool events throughout the year like their Storytimes. www.facebook.com/JeffersonOregonPublicLibrary
Scio
Roaring River Fish Hatchery- Bring quarters! This fish hatchery is a peaceful setting to watch fish in their different stages of growth. I love the monster trout in the big holding ponds. A great piggy-back off this trip is the Roaring River County Park. myodfw.com/roaring-river-hatchery-visitors-guide
Roaring River County Park- I discovered this place by accident on a drive once upon a time. It is a peaceful little park with a flat path along the river.
Lebanon
McDowell Creek Falls- there are stages of climbing long sections of stairs but it has been easily done with my littles, be ready to carry them up to the top though. There are several falls in this area, upper parking is good but lower parking is primary parking. The trail connection to cross the road can be confusing so pay attention. www.linncountyor.gov/parksrec/park/mcdowell-creek-falls
Santiam Excursions Train Rides- santiamexcursions.com/family-rides/
Lebanon Public Library- walk the complex and sometimes there are walk and read stories posted.
Corvallis
Osborn Aquatic Center- this is a great time to teach your littles how to swim and get comfortable in the water. If you go during "toddler time" it's a lot more laid back for one on one time with your kiddos. www.corvallisoregon.gov/osborn
Sweet Home
Rail Bikes by Santiam Excursions- santiamexcursions.com/railbikes/
Outside the Area
Oregon Coast Aquarium, Newport- aquarium.org/
Oregon Zoo, Portland- www.oregonzoo.org/
Wildlife Safari, Winston- wildlifesafari.net/
Cascades Raptor Center, Eugene- cascadesraptorcenter.org/
Roaring Rapids Pizza, Putt Putt Golf, Arcade, Eugene- roaringrapidspizza.com/