being a father of three, (11, 8, and 3 years old), i can definitely understand what you're going through. of course, you don't need kids to understand, as creative slowdowns can happen to anyone. but it's a fact that kids can drain your energy in a way nothing else can. and when you are down and exhausted at the end of the day, it's not always easy to see things through the lens.
despite also having a full time job in concept art, and a crazy schedule, i still managed to finish my second artbook three months ago. what i can see from my own experience here is that when you have a lot of contraints or obligations in your schedule, you tend to also organize things in the best way for your interest. for example i squeeze a lot more things in my time left, compared to friends and fellow artists and photographers who are unable to create the way they want, despite their insane amount of free time as well as younger age. it depends a lot on creative personalities, but if i have an empty schedule, lots of free time, and a bottle of cognac in the living room, i will have not much done. procrastination to the max! i turned 40 a few months back, so i am definitely not able to align 5 hours of work during night time or something, but i am still pushed and inspired to create, as i am always reminding myself the fact we've only got one life. not two. not three, just one. and clock is ticking.
with time, i learned to maximize the single hour i'll sometimes have at the end of the day, between 10:30 and 11:30 for example, or whatever time i have in front of me. and since you only have one, or two hours, you tend to NOT lose time!
another advice i would have is to be strict at when you want to have time off, and clearly inform your wife or family that at a very specific time, you will NOT change diapers, you will NOT do the dishes or whatever. you will have an hour for yourself. and if it's not shooting time, it can be anything else. but it's time to THINK. i think the advantage of this, at least for me, was that i was not only keeping the creative flow going on, but i was also more dedicated to the kids and family when i had just spent time for myself. it's like better dividing tasks. as artists, we all need this.
good luck Andrew,
i'll add more blurb and thoughts in they pop in my brain.
nic