My three are 13 (with additional needs and learning disability), 10 and 5 (both also have additional needs, but not as severe as eldest.
We all go upstairs at about 6.45ish. We play some board games altogether, then they all get into pyjamas.
Then 10 year old does music practice, 5 year old potters in his room with Lego/books while I get eldest to bed for about 7.45 (yes, early for a 13 year old but she wants/needs to go at that time).
Then I read to 5 year old while 10 year old endlessly faffs about (writing diary, rearranging 'precious' junk things, reading). Lights out for both 13 and 5 year old after this, so between 8-8.15.
I then spend 20 minutes or so with 10 year old, reading, playing a card game, talking stuff over. 10 year old can then read/draw/rearrange more stuff/do whatever and do own lights out (I check by about 9.30 and remind her to get some sleep if still up, but generally she's good about this).
I'm downstairs by 8.30 for some quiet time and general preparation for the next day, they are all upstairs mostly being quiet and going to sleep.
If separation is an issue, I'd be making a comfy corner in your dc's room, and trying to get across quiet/peaceful downtime before bed - stay in there, quiet pottering folding laundry etc, read a book, watch something on your phone/tablet (you only) - be there so dc is not alone, but minimal interaction (like settling a baby), trying to reinforce good bedtime habits then slow withdrawal (more pottering nearby, rather than in bedroom) etc.