I have a 2 year old and a 5 year old. It can be tough. I just have to go with the flow and follow my intuition. Sometimes the oldest goes to sleep first, sometimes the youngest. Sometimes we all go at the same time.
We usually do yoga or play some calming music, as well as books, and talking. Sometimes it's necessary to go for a walk around the block. Sometimes I let my oldest hang out in the dining room looking at books, coloring, drawing, etc. Sometimes I let her use the computer paint program or D.J. the youtube or Itunes music while I put the other to sleep.
Sometimes I'll put the oldest to sleep and let the youngest play with blocks or stuffed animals on the floor. It's definitely not a laughing matter. I used to make their dad come in to help me with them, even with him just being there doing nothing it was usually better than him not being there, but we are not together anymore.
We also make up lots of stories and talk about how to get good dreams and what to do in the morning and how much sleep we need and all the other kids that are sleeping...that helps with my oldest.