I need some advise on getting my 4 year old to sleep!......?

We have a soon to be 5 year old and a just turned 1 year old. We have twins on the way. This is the situation.....our 4 year old has to be coddled and coaxed to sleep every night. We have to lay with her which can takes forever! My husband has finally started falling asleep in her room and I have to go get him. When he quietly sneaks out of her room she is in our room w/in an hour. And this continues all night. I am sick of it. Our home will force the 1 and 4 year old to share a room and the twins will have to share a room. Any advise on getting the 4 year old to sleep on her own? Once the 1 year old is sharing a room w/ her I can only envision this chaos happening w/ 2 kids as the 1 year old will learn her bad sleeping habits. Also, any advise on transitioning a 1 year old to a new room and new bed! I am getting worried.