I write and work when my kids are sleeping. Otherwise, I don't have the patience or concentration to make sure the kids aren't into something AND keep my thoughts in order.
I do, however, jot notes down in a notebook through the day about certain changes or ideas I'd like to include in whatever project I'm working on.
Once I start a new book and have a solid idea, I take an evening or two to write a plan out - topics I want to include, length/format of th eboook I'm expecting, factor in how much time it should take to write, proof, edit, finalize, determine what supplies I may need, how long it will take to obtain them then I chop everything up into managable peices and try to keep on top of things.
I run a business along with writing, so I have to try and balance leftover housework with business and writing. I generally am not in bed before midnight every night (kids get ready for bed at 7, and are usually asleep around 7:30. I sit in the bedroom with them until they're asleep and usually read or bring a notebook in to write ideas down that I have flowing through my head).
We are expecting our third any time now, so I'm quite certain this whole idea of work when they sleep will go out the window for a while because my newborns never sleep at night (lol) but that's why I'm trying to finish projects so I have nothing pressing me when the baby is born. But eventaully I'm sure I'll get back into this cycle.