My kids are smaller, but because I lead a playgroup I have some ideas.
Oregon Zoo - $2 Tuesday on the 2nd Tuesday of each month
Sunburst Gymnastics (off Hway 212 a little past 82nd Drive) has open gym for school age from 12:15-1:15 on Tuesdays, for 2 kids it would be $4.50 I think, they also have Saturday morning open gym, not sure of the time
Ledding Library has Cultural Passes that would allow you to get in free to the Children's Museum up by the Zoo, the pass has to be reserved, usually about 2 weeks in advance
The Regal Cinemas up on the hill in Oregon City does free kids movies, I believe Tuesday & Wednesday morning at 10:00. Be there early, it's a popular one.
Barnes & Noble at Town Center has storytime with a craft, usually it is younger kids, but they might change that in the summer since kids are out of school
For a day when the budget isn't saying no, no, no (I hear you on that one) OMSI is great for kids to play & learn, right now they have a pretty cool dinosaur exhibit.
The Ceramic Cafe out on Sunnyside lets kids pick a piece, paint it, and fire it to keep. Cost can be anywhere from $6 to $60, so just discuss with your boys before-hand what the limit is.
Also, there is a magazine that comes out monthly that has a calendar of things that happen everyday. I can't remember what it is called, but I'll let you know when I remember, I need to get one now that spring is coming.
GOOD LUCK!!