I think your children are close to the max you could expect them to sleep (and you are very lucky) ; perhaps you should print this out and leave it laying around
My children are early risers in general, no matter what time they went to bed (not unusual for small children), so we have had to take some measures so we get some sleep. They each have room darkening curtains--ds (7.5) has ADHD and problems getting/staying asleep so he had them first; we got them for dd (5) because she was getting up at the crack of dawn and we want to be able to sleep until 7am on weekends (Target has some less expensive, shorter, and "child friendly" colors, Walmart has some thicker, more expensive, but very good darkening curtains). Last night we put them to bed at 7pm because dd has a mild cold and ds was coughing a bit; ds was up around 5am and I woke dd up, though it was easier than normal. When I was little I would get up around 6am on the weekends.
Currently, we try to get them to bed by 7:30pm and they wake at 6am to get ready for school (leave with dh at 7:15am)--if I don't have dh to help (sick or doing homework) I usually can't herd them to bed until 8pm. Ds is ok with 10hrs sleep but I think dd could use 11hrs.