M.D.
I have the same situation, similar aged kids. Same problem!
I tried giving up the nap and quiet time, but that was a total disaster.
Now we do quiet time/nap time. They can play, read book, play leapster as long as it is quiet & in their room, together or apart.
It helps us get through the rest of the night, but it is tough.
Everyone is up to bed at 7.30 fpr the night time routine of brushing teeth, reading books, songs. I am done by 8 or so.
Quiet time help all of us, including me so hang onto that at least.
She will occasionally nap if I lay with her, but then the night goes much longer.
So I've found either no nap, then rough night but it is over at 8. Or nap and the night goes till 9 or 10.
I've chosen the no nap route so I can have some time to myself at the end of the day.
Good Luck!