Showering: I found a toddler plastic fence, and made a "yard" outside the open bathroom door, put in playthings for dd. She was content. Never let her be about the house by herself... toddlers are unpredictable... accidents happen noiselessly sometimes.
Letting them be up without you, look after themselves... maybe promotes independence--that's a good thing. Kids though... the fact is, that they will quickly identify the times they can do what they are not allowed to do while you're on alert... just because you don't know what they're up to does not mean that they aren't up to trouble. I'm sure you and your sisters are very good mothers, but just because nothing's happened... is it a good idea to not wear seat belts since no one in your family has ever been in an accident? No one in my family had been, and then I was hit head-on at high speed by a one-ton truck, whose grill my body would have been tangled in had I not been wearing a belt.
Your six year old is probably developing a "little mother" or "little father" personality as he/she is kind of "in charge" of younger sibs. That's kind of the way I was raised: my older bro kind of took charge when parents were not right there. That's not a bad thing, usually. Maybe the eldest left in charge gets saddled with a certain amount of responsibility that may be a bit premature, and that makes them a different adult. Good? Bad? Who can judge? It depends on their personality, their genetics, their environment. We're all different, responding to different cues. You do what feels safe... and you can always change your mind or alter your approach if it's indicated based on cues your kids give you.
My seven-almost-eight year old gets up without me... since age fivish, I've always left fresh fruit, bite-sized cut, for her to get her own snacks when I was right there. I'd have my coffee, and let her serve herself with what I'd prepared the night before. We'd be together, but she'd be serving herself. By the time she was six, I was letting her get up and feed herself while I slept a little longer. I had her well-habituated to fruit and/or cereal in the morning, and laid out irresistible projects to occupy her if I knew I was hoping to sleep in.
Trust your intuition. Abuse... no. Abandonment... well, yeah. If they got hurt while you were sleeping, the public interest would not be supportive, I'm sure, no matter who else also sleeps while their little kids play in the house. But if they don't get hurt, who's to know?
Oh, and one more thing. I used to be a light sleeper. A really light sleeper. And then, I realized that I am not a light sleeper anymore. Something to consider. You don't know when you stop being a light sleeper until you hear about the noise that actually occured while you were sleeping "light."
I like your name... Aura Kitten.