I think most children inherently want to be helpful, they've just never been taught how to be.
My girls watched me cook via the 'chair' method when they were small as well.
One was particularly hardheaded about trying to touch the stove while I was cooking. After about the 15 millionth 'Don't touch it, it's hot', I let the stove cool off considerably. When she reached for it (looking at me the whole time, of course) I told her 'Go ahead! You want to touch it, then touch it, but it's hot!"
She did, yanked her hand back, and tears welled up in her eyes. I told her not to even think about crying, because I'd told her repeatedly NOT to touch it.
The older twin loves to cook to this day. She made a chocolate layer cake last weekend that was scrumptious!
I just can't believe they turn 11 on Monday!
Well, Happy Birthday to your twins! And may they have many, many more!
And, isn't it amazing that if you don't expect much of them - they're happy to oblige. But if you teach and then challenge them - they will absolutely amaze you!