My daughter still took daily naps until 1st grade. She needed it, would be tired, and still went to bed at night fine. Bedtime being 8:00-8:30.
She would nap afterschool.
My son, is 3 now. He is napping right now. He still takes naps everyday. He needs it, gets tired and naps. It is a daily routine. Today he even told me he is tired and is going to nap, and just went to his bed to lay down.
Both my kids, no matter what time they go to sleep at night... will wake up at the same time in the morning no matter what. It is "their" clock. I was not one who manipulated their bedtimes at night to make them wake up later. I figure, that is the way they are. They wake at a certain time in the morning, regardless. They were that way since babies.
My daughter is now 7. If she is tired afterschool or what not, she will still nap. I don't force it. My son still naps everyday. They both will nap in the afternoons. OR, it is quiet time. But they usually nap no problem. BECAUSE I have a daily routine for them. They know it like auto-pilot. I don't force naps... but I know their cues and when they are tired. And they get into their routines, and will nap. AND, I also tell them Mommy is going to nap too... and then I lie down. It is a routine.
And yes, if one kid is napping and the other(s) are not... then you need to have them be quiet. My kids KNOW that if one is napping and the other is not, they NEED to be quiet, so they don't wake them up. And they do do quiet things. Its a "rule" they understand. And yes, that means "you" do not have a down-time nor alone time. Because you need to be up with the child that is not napping. OR, you tell that awake child, that it is "quiet" time... and you BOTH do quiet things... or you tell your child that you are going to do "work" and he has to do quiet things too. With my kids, that works.
Both my kids nap for about 2 hours. Their timing. Not mine.
All the best,
Susan