Boredom Busting Summer Activities for families with TWO young kids

The lazy and fun days of summer are already coming to an untimely and unwelcome close here in our household. Rearing it's ugly head is the BORED and IRRITABLE monster's, better known as my kids. As they get older, the arguments and competition get bigger and more unruly, and I am at a complete and utter loss as to how to handle it. Both kids have a weekly commitment (one does dance and one does karate), but it apparently is just not enough for them to keep them occupied and focused enough for the whole week. So I am gathering ideas on what to do to keep them busy and their minds exercised, while we await the start of the Fall 2012 school year in just over 3 weeks. I have scoured the internet for "Boredom-Busting-Brain-Benders" and here is what I found.

1. Find a new playground/park.
2. Go to the beach. (dinnertime is my favorite time to visit the beach. there are less people there, it's not as hot, and bathing suits aren't necessarily required)
3. Visit Storytime at your local library. (call ahead or check their website first, some libraries change their kids activity scheduling in the summer)
4. Go digging for fossils. (find a patch of dirt and have the kids dig for rocks)
5. Bake. (my kids love cooking up something in the kitchen. And if they help cook it, they are more likely to eat it!)
6. Date Night with Mommy/Daddy. (one-on-one time can do wonders for a kids attitude)
7. Clean out the basement. (the kids will find hidden "treasures" and you will get a de-cluttered basement. Be sure to toss/donate everything you don't need. The more you get rid of, the better you'll feel!)
8. Screen time. (I know some mom's aren't a big fan of the TV/Video Games, but if ONE child is occupied with a movie/tv show/video game, you can give the other child special attention to work on a craft or project JUST FOR THEM!)
9. Summer Movie Specials. (Two of our local theaters participate in summer movie deals. Where weekdays (or SOME weekdays) they play a FREE or $1/ticket kids movie at 10am. They also have kids meals for only a few dollars. With the oppressive heat of the Chicagoland area this summer, these have been lifesavers for us!)
10. Ship 'em off to Grandma's. (My 5yo loves special time with his grandparents. It's kind of like Date Night with Mom/Dad, but he usually spends the night and gets all their love and attention for a longer amount of time. My 3yo isn't quite ready for an overnight without Mommy, but when the time comes, she will be spending some nights with her grandparents too.)

How do you beat the summer boredom? Please share!