Working myself out of a job

I'm trying to teach my kids to take responsibility for their stuff and try solve their own problems.  The biggest obstacle is putting aside my own control issues and letting them make mistakes so they can learn how to deal with them.  I had a prime opportunity today.

The kids take a science class on Tuesday mornings. They have a take-home test once a month.  They have a week to finish it.  Ideally, my responsible kids would make sure they finished the test on time.  But they need help scheduling their time (they're kids, after all), so I write it on the whiteboard to remind them.  Today I wrote "Finish science test" on the board.  Noah said he couldn't find his.  I gave him the speech again about keeping all his science stuff in his science bag.  Then I started mentally solving the problem of the missing test.  I caught myself and realized that this is HIS problem, not mine, I asked, "What are you going to do about your test?"

N: I don't know.  What should I do?
M: What COULD you do?
N: Mom! Just tell me!
M: I want you to think about it instead of just expecting me to fix it.
N: I guess I could ask the teacher tomorrow for another one.
M: You'd have to ask her today, because it's supposed to be finished by tomorrow.
N: I can't call her!  I don't know her phone number.  She's probably not home.
M: What else could you do?
N: Well...you could copy the questions from Sarah's test...
M: I don't have the time or desire to do all that writing. [He's starting to get upset, so I offer a suggestion].  Maybe you could call your friend in the class and see if he's done his yet.  If it's still blank, you could make a copy of it.
N: Ok, I'll call him.  Thanks for the idea!

He calls, and the kid hasn't started his test (I guess mine isn't the only procrastinator). I consider making Noah ride his bike to his friend's house and then to the library to make the copy, but I think that would cross the fine line between teaching responsibility and being mean and unmerciful.  So I tell him that I'll drive him but he needs to bring his own change for the copy machine. 

N: How much is a copy?
M: I think it's a dime a page.
N: I don't have a dime.
M: Hmm.  What are you going to do?
N: Mom!
[Interlude of silent staring at each other}
N: I have a quarter.  Will that work?

So off we go to the friend's house, pick up the test, arrive at the library, and he says, "I lost my quarter."  I have nothing nice to say to that, so I leave him in the car and go in the library, taking deep breaths on the way.  Eventually he appears with the quarter and stands around helplessly.  I point to the copy machine.  He tries to hand me the test, but I think it's a good time for him to figure out how to use the copy machine.  I end up helping him a lot, but he's never used a copy machine before, so that's to be expected.  I drive him back to his friend's house to return the test, and we go home. I hope he's working on his test now.  The whole experience was time consuming and frustrating for both of us, and I never know if I'm doing the right thing or not.  I tend to err on the side of doing too much for the kids.  I must force myself to step back and let them make mistakes.