Are you planning to adopt through a private agency or from the state care system?

Private adoption experiences vary so I can't speak about those, but the state will assign a social worker who will check on you. That person getting wind of your grow would be bad in ways we can both imagine, and I fear that the danger of discovery is higher than you've estimated. I don't want to sound discouraging - adopting is awesome! I have experience with the process by proxy after watching a relative go through it, and analyzing the situation makes me worry that the logistics of your grow might need to be altered if you are adopting kids out of state custody:

The problem is the fact that you will not be able to hide what you are doing from the kids for long if it takes place in the house or yard. I know you intend to educate them, but 5-10 year olds are unpredictable and all it takes is one mention or hint of MJ in a checkup interview to start a firestorm.
If a kid catches you smoking/harvesting/etc, you could:

1. Act as though it's not something significant. "It's my medicine, hon." "Oh, ok."
This runs the risk that the kid will innocently blurt it to the caseworker, babysitter, etc. Caseworkers are trained to keep their antennae up for things like this.

2. Make the kid aware that, while not bad, it's something that needs not to be discussed publically (follow up with the book and explanation)
If the caseworker drops by on the day you confiscated the kid's favorite action figure, he might tell your 'secret' to spite you. Even the nicest kids have their 'moments,' and they don't grasp legal consequences.

3. Explicitly explain the legal consequences. Warn the kid that if he tells about what he sees, the government will take him away.
Possibly effective, but EVIL!! :vader1:

Smoking discreetly shouldn't be much of a problem, but I truly suggest that you move the grow op somewhere away from the house. If you sit on a large plot of land, a locked, insulated shed in a corner of the property might work, as might the house of a trusted friend who wouldn't mind making it a tandem effort. In time (years), when caseworker oversight has lessened and you've grown into a family it'll be far less of an issue, but for now, healthy paranoia!