What time fo your kids go to bed? Ours go to sleep between 7:30pm and 8:30pm. This gives me a few decent hours before I go to bed (honestly about 4) to do things I want or need to. I have several friends that let their kids stay up until 10 or later and then complain they never have time to themselves or alone with their SO. Routine bedtime has benefits for us :)
Are the kids old enough to help around the house and save you some time? Setting the table, clearing the dishes, wiping off the table after meals, picking up toys, etc. My 5 year old helps straighten, yesterday we were doing yard work so I offered him a nickle for every large stick he found over 18 inches. Getting the kids involved.. I'm hoping to make good habits now!
Are there any time saving techniques you could utilize? Slowcooker for dinners, freeze and fix meals? Carpools for things for the kids?
As to the walking.. I have a gym membership that includes daycare. I reward myself with a soak in the hottub.. and somedays I just go for the hottub (hah!) You might also consider taking the kids with you for your walk -- help wear them out and make bedtime easier.
My personal advice? Don't try to be "super Mom" - with the spotless house and shiney toilet. I have three kids - sometimes things don't get done that day. It's not the end of the world. Be a super Mom to your kids and take care of yourself. Your kids won't grow old thanking you for how clean their toilet was.