op this is what happens in our house(i have older ones too so at the same but i do have a baby 6 months too)
dh gets home at 6,I try to get dinner ready for this time so we can all eat together.
After dinner,we all go upstairs,dh is in charge of bathtime while i tidy the dinner stuff away.
I put dc3 and 4(3 and 6 months)to bed,when i say i put them to bed,i lie with them in my (superking size)bed ad they fall asleep,can be a few seconds if they are really tired,could be about 20 minutes,its not usually longer than that,maybe you could orchestrate your babies naps so that hes tired enough to go to sleep in a decent amount of time, hours is a long time.
While i do this dh is doing the same with dc1 and 2(5 and 4)iit takes about the same amount of time.
After this is our child free time,so we do what we want,sometimes the baby wakes up and ill go and sort him out,sometimes ill brig him downstairs if i want to.
We have lots of sex,which is why i am always pregnant lol!