Mama, my boy too is a night owl, I put him to bed at 9:30 on a school day and at 11:30 I still hear him make airplane/explosion noises, dont' matter to me, rules are rules and he knows he is supposed to stay in bed. We put some soft music and keep it quiet, even if we aren't doing it, we just want sometime alone. I have a 3yr old who follows me to the bathroom, I work full time and miss her so, but still, bedtime is bedtime and she knows this, after her milk, brushing of teeth and book she goes to her bed, lights out, and she stays there, both kids know they aren't supposed to be out and about after I tuck them in and I'm consistent, no kids awake after 10pm.
Long ago I used to let kids stay up 'til 11, again, because I didnt' see them during the day, and so H and I never got time alone, it contributed to our distancing.
So what if the 9 and 11 yr can "guess" what you are doing, you are adults and it is normal--you are not doing drugs or something illegal-- it's nothing to be ashamed of. Walk your little self to Home Depot TODAY and 12$(more of less) later you'll have some privacy, anyone can change a knob.
Be not afraid...I will repay you for the years the locusts have eaten Joel2
30something 2kids survivor of S, MLC, A, D I have peace in my heart, at last.