Do kids sleep at really sleep at night?

My kids are still both awake and have been in there room for 2 hours now. No one is crying or fussing, they are just in there playing. I drive myself crazy going in there and threatening them to go to sleep. Greg tells me to just leave them alone, they will go to sleep when they are ready. However, if I leave them alone it may be 1:00 before they go to sleep. Should I drive myself crazy over this, or just put them in there at bed time and let them play until they are ready to sleep? This isn't a rhetorical question, I am truly looking for advice.

I can't really come up with a good reason to stress out about this. I mean when they go to sleep, they sleep all night. They don't wake up until around 9:00 and since we don't have anywhere that we have to be early, what's the problem with that. Should I just chill out and push their bedtime to later? During the day they are typically sweet children. I mean we aren't having temper tantrums due to lack of sleep and they usually nap very well for me. Well, I should say Matthew does. He is a lot like dad and could sleep all day long. Katie is more like me and afraid she is going to miss something if she goes to sleep. I am having to work real hard to keep her from dropping her nap all together. I personally really need them to keep napping. I need the short break in the afternoon.

Anyway, if anyone can help me I would love it!