I love helping ds with stuff like this but have to really control myself!! Here is where I allow myself to offer help - if he is trying to build something which requires a completely new technique he has never tried, I give him some examples, we build a small prototype or something like that.
I definitely still do dangerous cutting, soldering, things of that nature so he doesn't kill himself. Kids work is usually not what "I" would do...but usually he gets really good comments and feels ok about things. Often he does things I'd never ever think of doing. He did a king tut model last year, I really really thought he should make this model from 1 big piece of cardboard to avoid falling apart but he insisted on making it out of several... he did it his way and it turned out to be really cool because of that decision - the burial mask could come off completely and you could see old Tut's shriveled face, and the arms moved a bit too.
I couldn't see what was in ds' head when he started, but in the end it was all clear.
At age 7, I think it is reasonable for there to be a disconnect from what the child wants to make and what they understand about the materials, etc. in order to complete the project they have envisioned. I think for gt kids especially this divide is going to be a big gap and offering technical help seems completely acceptable. I understand other folks might disagree...
