I need some bed/naptime suggestions

[Sarah8914]

So, my almost 4 year old will go to sleep by 8:00 every night if she doesn't have a nap that day. It's been awhile since she stopped being consistent with naps. I replaced naptime with quiet time and about half the time she falls asleep. Well, the problem is that if she takes a nap, she is awake until 10 (in her room, but awake). If she doesn't take a nap, she's a little grouchy and tired, but goes to bed much better.

Now this wasn't an issue too much before because she had her own room. Now her little sis (almost 2) shares with her and if Kathryn stays awake until 10, she keeps Hannah up too.

Sometimes I wake her up from a nap after a few minutes so she won't sleep, but I know she's tired. Any ideas for me? Should I never let her nap? Should I not worry about it? Should I put the little one down first and hope the older one doesn't wake her up when she lays in bed forever?