I don't have that seven year old but I WAS that seven year old! This was the routine my mother put in place when I was eight that had me going to sleep at better times, sleeping longer etc within about 2 weeks. This is a routine I still follow, to some extent in adult life.
- ROUTINE: every late afternoon do something which involves exercise. Brisk walk, run around the park. Swimming. If the weather's bad they can help with cleaning and tidying eg do the vacuuming!. (My mother had a very clean house). This breaks the "overthinking" pattern kids who worry and think a lot can get into, and both refreshes and exhausts them at the same time.
No television/playing with toys/scrapping with siblings in the hour before official bedtime.
Meditation. This is quite a fun one you can do if you put more than one kid to bed at similar times. You can get a relaxation tape on amazon or do it without. For ten minutes, everyone sits cross legged on the floor and tries to empty their minds. Give them each a word and tell them to repeat the word in their heads over and over.
After that is a good time to encourage a worrying child to talk over anything that it is troubling them.
Then bed. Big light off, side light on and BOOK. BOOK is absolutely crucial. Every night, twenty minutes reading by themselves, minimum.
Make it clear to them that it doesn't matter if they aren't actually asleep so long as they are resting. This is something I still tell myself now to wind down if I am anxious about not getting to sleep.
At lights out time, they turn their light off and try to go to sleep. They should give it fifteen minutes, with their eyes shut. If they are still awake after fifteen minutes they can turn their light back on, but only to read and then have to try to get back to sleep fifteen minutes later. And repeat...
If thoughts or worries are troubling them get them to develop a mantra. "This is a thought for another day. I will shut my eyes and it will go away". Or something like that. Every time they feel troubled by a thought when trying to sleep they repeat it.